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Bio-organic Research Laboratory, Departm

Delhi-110 007, India. E-mail: smschau

27666845; Tel: +91-11-27666845; +91-9871

† Electronic supplementary information (of all new compounds. 125Te and 77Se NMspectra of porphyrinogens in the presencethe presence of Hg2+. CCDC 932049. Forother electronic format see DOI: 10.1039/

Cite this: RSC Adv., 2014, 4, 3171

Received 8th November 2013Accepted 2nd December 2013

DOI: 10.1039/c3ra46491a

www.rsc.org/advances

This journal is © The Royal Society of C

Synthesis of 5,10,15,20-meso-unsubstituted and5,10,15,20-meso-substituted-21,23-ditellura/diselena core-modified porphyrinogens: oxidationand detection of mercury(II)†

Sohail Ahmad, Kumar Karitkey Yadav, Sarangthem Joychandra Singhand S. M. S. Chauhan*

Tellurium and selenium incorporated 5,10,15,20-meso-unsubstituted-21,23-ditellura/diselena core-

modified porphyrinogens (N2Te2 and N2Se2), 5,10,15,20-meso-unsubstituted-21-tellura/selena core-

modified porphyrinogens (N3Te and N3Se) and fully substituted meso-carbons porphyrinogens

(N2Te2, N2Se2 and higher analogs) are synthesized by 3 + 1 condensation of tellurophene/

selenophene dipyrranes and their corresponding diols in the presence of BF3–etharate or BF3–

methanol. The meso-unsubstituted and substituted porphyrinogens were oxidized with chloranil/0.1%

aqueous FeCl3 in CHCl3 at room temperature to obtain the corresponding porphines and porphyrins

which are further reduced to corresponding chlorin and bacteriochlorin, whereas the fully meso-

substituted porphyrinogens were found to be good ligands for Hg2+. The structures of the products

were characterized by IR, 1H, 13C, 125Te, 77Se NMR, CHN analysis, mass spectrometry and single-

crystal XRD.

Introduction

Porphyrinogens (calixpyrroles) are a class of tetrapyrrolic mac-rocycles composed of four pyrrole rings linked through themeso-positions by carbon atoms. The b- and meso-positions inporphyrinogens are reactive positions at which suitablesubstituents can be introduced to tune the properties of theporphyrinogens for specic applications. Fullymeso-substitutedporphyrinogens are stable and have been used in anionbinding,1 detection of various explosive1f and self-assembly,1

while meso-unsubstituted porphyrinogens have remainedunexplored due to unstability and complexity in synthesis.2

Meso-unsubstituted porphyrinogens are highly desirablesynthetic precursors for the construction of meso-unsubstitutedporphines3,4 and other complex systems with special physicaland chemical properties.3b,5 Porphines/porphyrins of porphyri-nogens are used as a starting material for various newerporphyrins.5 These are further utilized for the synthesis oflonger-wavelength absorbing5c–e and uorescing molecules such

ent of Chemistry, University of Delhi,

han@chemistry.du.ac.in; Fax: +91-11-

969266

ESI) available: 1H and 13C NMR spectraR spectra of all porphyrinogens. UV-Visof Hg2+. 125Te, 77Se NMR of 5g and 5h inESI and crystallographic data in CIF orc3ra46491a

hemistry 2014

as chlorins, bacteriochlorins and purpurins which are poten-tially used as uorescence imaging or phototherapeuticagents.5f–i

A wide variety of porphyrinogens with donor atoms (O, S, Nand P) containing nonpyrrolic arene units,6–9 have beendesigned and synthesized to modify the binding ability of theporphyrinogens. The 5,10,15,20-meso-octamethyl-21,23-dithia-porphyrinogen (N2S2) and 5,10,15,20-meso-octamethyl-21-thia-porphyrinogen (N3S) ligands containing nitrogen–sulfur donoratoms are highly selective complexing agents towards heavytransition metal ions (HgII, CdII and AgI).10 Therefore, a similardevelopment is anticipated for the porphyrinogen with heavierchalcogen donor atoms such as selenium and tellurium, due totheir ‘soness’ and better sigma-donor capacity as compared tothe lighter group 16 congeners.11 The synthesis of selenium andtellurium 21- and 21,23-core-modied porphyrins,12,3b in whichone or more heteroatoms replace some of the four nitrogenatoms, has been already reported with altered core sizes, metalion binding properties,12 reactivity12 and redox potentials.12

Herein we report the synthesis of novel meso-unsubstitutedTe/Se core-modied porphyrinogens and meso-substituted Te/Se core-modied porphyrinogens via acid catalyzed 3 + 1condensation of corresponding tellurophene/selenophenedipyrranes and diols. The meso-unsubstituted porphyrinogensare further oxidized to their corresponding porphyrins andporphines, whereas the meso-substituted porphyrinogens wereutilized for the complexation of Hg2+.

RSC Adv., 2014, 4, 3171–3180 | 3171

Scheme 2 Synthesis of core-modified porphyrinogens.

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Results and discussion

The desired 2,5-bis(2-pyrrolylmethyl)tellurophene (dipyrrane)4a was synthesized in three steps starting from prop-2-yn-1-ol(1a). The reaction of prop-2-yn-1-ol 1a with CuI and NiCl2$6H2O,followed by the addition of TMEDA in THF under aerobiccondition,13 proceeded smoothly to afford the diynediol 2a in93% yield. The solution of diynediol 2a and AgOAc inMeOHwasadded to aqueous solution of Na2Te14 to afford tellurophenediol 3a in 85% yield. The tellurophene diol 3a reacted withexcess pyrrole in the presence of BF3–etharate to afford dipyr-rane 4a in 75% yield. The other dipyrranes (4b–h) weresynthesized via similar route (Scheme 1).

N2Te2 and N2Se2 5,10,15,20-meso-unsubstituted and5,10,15,20-meso-substituted-21,23-ditellura/diselena core-modi-ed porphyrinogens (5a–i) were synthesized by following thetwo methods A and B (Scheme 2).

The meso-unsubstituted and meso-tetramethyl core-modiedporphyrinogens (5a–d) were prepared by 3 + 1 condensation ofone equivalent of dipyrranes (4a–d) with one equivalent of cor-responding diols (3a–d) in the presence of BF3–methanol usingdichloromethane as a solvent (3.2 mM) at 0 �C for 1 h, followedby stirring the reaction mixture to room temperature for 45 min(method A). The crude porphyrinogens were puried by silicagel column chromatography to afford white solids 5a in 15%, 5bin 11%, 5c in 27% and 5d in 22% yields respectively. Theappearance ofmeso-methylene protons (meso-CH2 for 5a, 5b andmeso-CH for 5c, 5d) at about d 3.92–4.04 ppm as a sharp singletin the 1H NMR spectra and a corresponding m/z peak in themass spectra conrmed the formation of ditellura/diselena core-modied porphyrinogens (5a–d). An attempt to collect X-raydiffraction data was unsuccessful because of the poor qualityof crystals. Four unsubstituted meso-carbons porphyrinogens

Scheme 1 Synthesis of tellurophene and selenophene dipyrranes(4a–h).

3172 | RSC Adv., 2014, 4, 3171–3180

(5a and 5b) are highly unstable and are very difficult to handleand become dark at room temperature in comparison to 5c and5d porphyrinogens. Interestingly the above reaction conditionsfavor the formation of cyclic tetramers but their higher cyclicoligomers and N-confused products were not obtained. Toobtain the higher analogue, the reaction of dipyrranes (4a–d)with corresponding diols (3a–d) in higher reactant concentra-tion (5.3 mM and 16 mM) in dichloromethane or acetonitrile at0 �C were carried out and it afforded a polymeric oxidizedproducts along with small amount of porphyrinogens. In mostcases, the N-confused cyclic tetramer, hexaphyrinogen andoctaphyrinogen could be detected only on TLC as they arereadily oxidized to the dyes without isolation. Porphyrinogenswith phenyl group (5e–f) were detected only on TLC andwere notisolated, as they are readily oxidized to corresponding porphy-rins during the workup procedure and mixtures of porphyri-nogens and porphyrins were obtained. Even isolatedporphyrinogens from column purication are readily oxidized tocorresponding porphyrins.

The porphyrinogens 5a–f were oxidized with chloranil inCHCl3 at room temperature for 10 min to obtain the corre-sponding porphines and porphyrins or by shaking the por-phyrinogens solution with 0.1% aqueous FeCl3 solution for10 min (Scheme 3). Prolonged shaking or stirring the reactionmixture caused decomposition of the product, whereas theporphyrinogens with 0.1% aqueous FeCl3 solution in shorterexposure times were not oxidized to the product. However,

Scheme 3

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attempts to oxidize the porphyrinogens 5a–f with DDQ led tocomplete decomposition. The high resolution mass spectrom-etry showed corresponding m/z peak to porphyrin/porphinealong with porphyrinogen peak (see ESI†). The correspondingporphyrins of porphyrinogens 5a–c are unstable and readilyundergo to decomposition at room temperature. Porphyrinogen5b on oxidation with 0.1% aqueous FeCl3 solution gave unstableisolable novel 21,23-diselenaporphine in 5% yield, whileoxidation with chloranil gave 2% of porphine. In the 1H NMRspectrum of the 21,23-diselenaporphine, the meso protonappeared at d 10.49 ppm, while pyrrolic and selenopheneprotons were appeared at d 9.36 ppm and 10.29 ppm, respec-tively. The electronic absorption spectra of 21,23-dis-elenaporphine was recorded in CHCl3 and a soret along with Qbands were observed at 415, 474, 504 and 535 nm. Porphyri-nogen 5d on oxidation with chloranil gave stable novel5,10,15,20-meso-tetramethyl-21,23-diselenaporphyrin in 76%yield. In the 1H NMR spectrum of the 5,10,15,20-meso-tetra-methyl-21,23-diselenaporphyrin, the meso methyl group (CH3)appeared at d 4.5 ppm, while pyrrolic and selenophene protonswere appeared as singlet at d 9.2 ppm and 10.1 ppm, respec-tively.15 The electronic absorption spectra of 5,10,15,20-meso-tetramethyl-21,23-diselenaporphyrin was recorded in CHCl3and four Q bands along with one intense soret band wereobserved at 693.5, 630.0, 554.1, 521.8 and 437.8 nm. The elec-tronic absorption spectra of corresponding porphyrins of por-phyrinogens 5a–d are given in ESI.† Porphyrinogens withphenyl group (5e and 5f) were oxidized with DDQ to corre-sponding porphyrins in 86–90% yield, which were characterizedand matched with the spectrum of 5,10,15,20-meso-tetraphenyl-21,23-ditellura/diselenaporphyrin.12

The N3Te and N3Se porphyrinogens with four meso-unsub-stituted carbons can be used in constructing highly desirablenovel 21-tellura/selenaporphyrinogens systems. The N3Te por-phyrinogens 9a (Scheme 4) were synthesized from the unsub-stituted diols (3a) and 2,5-bis(2-pyrrolylmethyl)pyrrole(tripyrrane) in the concentration of a 3.2 mM scale (method A),affording 9a (7% yield) and 9b (8% yield). 2,5-Bis(2-pyrro-lylmethyl)pyrrole (tripyrrane) was obtained by formylation ofpyrrole followed by condensation with pyrrole of the resulting2,5-bis(hydroxymethyl)pyrrole in the presence of acid.2a In the1H NMR spectrum of 9a in CDCl3 at room temperature, meso-methylene protons connected with a tellurophene ring andconnected with a pyrrole ring appeared at d 3.99 and d 3.86 ppmas a sharp singlet, respectively. The N3Se porphyrinogen 10awas prepared in the same manner, affording 10a (11% yield)

Scheme 4

This journal is © The Royal Society of Chemistry 2014

and 10b (traceable amount). An attempt to obtain 21-tellura/selenaporphine by oxidation of 9a and 10a were carried out byshaking the porphyrinogens (9a and 10a) solution with 0.1%aqueous FeCl3 or addition of chloranil directly to the reactionmixture at room temperature for 10 min, but it led to theformation of a complex mixture and even in HRMS no peakcorresponding to 21-tellura/selenaporphine were detected.

The absence of steric hindrance in meso-unsubstitutedselenaporphine and meso-tetramethylselenaporphyrin offersthe further utilization of these compounds. The reduction ofselenaporphine/porphyrin were carried out by using p-toluene-sulfonhydrazide in the presence of pyridine and potassiumcarbonate to synthesize novel phototherapeutic modelcompounds diselenachlorin and diselenabacteriochlorin(Scheme 5). Reaction of the 5,10,15,20-meso-tetramethyl-21,23-diselenaporphyrin with 10 equivalent p-toluenesulfonhydrazideand 10 equivalent K2CO3 in pyridine for 24 h, gave meso-tetra-methyldiselenachlorin and meso-tetramethyldiselenabacterio-chlorin in 5% and 2% yield respectively. The correspondingchlorin and bacteriochlorin of meso-tetramethylselenapor-phyrin are unstable and readily undergo decomposition at roomtemperature. The formation of meso-tetramethyldiselena-chlorin was conrmed by the appearance of reduced pyrrolicproton at about d 4.29 ppm and d 4.60 ppm as triplet in the 1HNMR spectra. The selenophene and pyrrole protons of dis-elenachlorin are upeld shied with respect to selenapor-phyrin. The selenophene protons were appeared as doublets at d9.27 and 9.64 ppm (J ¼ 4.8 Hz) while pyrrolic protons appearedas singlet at d 9.07 ppm. The electronic absorption spectra ofmeso-tetramethyldiselenachlorin (soret and Q bands wereobserved at 437.9, 522.6, 550.8, 631.7 and 689.0 nm) was moresimilar to the starting material. However, the longest wave-lengths absorption (689 nm) is more intensied and 4 nmhypsochromically shied compared to the starting meso-tetra-methylselenaporphyrin. The 1H NMR spectrum of meso-tetra-methyldiselenabacteriochlorin is much simplied due tosymmetrical structure of bacteriochlorin. The selenophenesignal is downeld shied and appeared at d 8.92 ppm assinglet. A comparative shi for the reduced pyrrolic protons wasalso observed. The UV-vis spectrum of the meso-tetramethyldi-selenabacteriochlorin, shows three-bands at 408, 535, 739 nm,in which the longest wavelengths absorption is signicantlymore red-shied (739 nm) as compared to the correspondingchlorin (689 nm) and selenaporphyrin (693 nm).

An attempt to obtain chlorin by reduction of 21,23-dis-elenaporphine (meso-unsubstituted porphyrin) using p-tolue-nesulfonhydrazide, led to the decomposition of starting

Scheme 5

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material or product and no corresponding chlorin was detectedin UV-Vis spectrum. Selena/telluraporphyrins with phenylgroup at meso position are less prone to reduction and requireexcess of the reducing agent and longer reaction time. Thereaction was monitored by TLC and UV-Vis spectroscopy.

The fully meso-substituted core-modied porphyrinogens(5g–i) were synthesized by condensation of dipyrranes (4g–h)with corresponding diols (3g–h) in the presence of BF3–etharatein dichloromethane (3.2 mM concentration) at room tempera-ture for 30 min (method B). These porphyrinogens (5g–i) arehighly stable and can be stored for over 1 year at roomtemperature. To obtain the higher analogue (Fig. 1), similarreactions were carried out in acetonitrile at 0 �C with the sameconcentration (�3.2 mM) but not much difference in cyclictetramer yields were observed and no higher ordered specieswere detected (Table 1). The increase in reactant concentration(�16 mM) favored the formation of higher ordered species andgave 5g in 23% yield, N-confused cyclic tetramer (6g) in 5%yield, hexaphyrinogen (7g) in 13% yield and octaphyrinogen(8g) in 11% yield. Increasing the concentration upto 81 mMgave hexaphyrinogen (7g) and octaphyrinogen (8g) as the majorproduct. The formation of hexaphyrinogen (7g) involves thecondensation of diol (3g) with twomolecules of 4g, in which oneof the 4g undergo pyrrolic group cleavage under acidic condi-tion and followed by subsequent cyclization gave hexamer.16

Further the nature of other acid catalysts were investigated in

Fig. 1 Structure of N-confused and expanded porphyrinogens.

Table 1 Yield of the condensation reaction between 3g and 4g in dryacetonitrile in different reactant concentration and in the presence ofdifferent acid catalysta

EntryConc. ofreactant (mM) Catalyst 5gb 6gb 7gb 8gb

1 3.2 BF3$OEt2 41 0 0 02 5.3 BF3$OEt2 42 0 0 33 16 BF3$OEt2 23 5 13 114 40 BF3$OEt2 15 7 19 175 81 BF3$OEt2 10 10 26 216 3.2 TFA 42 0 Trace 07 16 TFA 19 3 16 108 3.2 MeSO3H 43 6 0 09 16 MeSO3H 41 8 3 16

a Reaction condition: 3 g (0.5 mmol), 4 g (0.5 mmol) and acid catalyst(0.092 mmol) at 0 �C for 30 min. b Isolated yields in percentage (%).

3174 | RSC Adv., 2014, 4, 3171–3180

two different concentrations 3.2 mM and 16 mM. In 3.2 mMconcentration, the above reaction in halogenated acid such asTFA and in nonhalogenated acid such as methane sulfonic acid,exclusively gave 5g. While the same reaction in 16 mMconcentration, 5g, 6g, 7g and 8g were obtained in 19%, 3%,16%, 10% yields respectively in TFA, whereas with methanesulfonic acid 5g and 8g were obtained as the major products(Table 1). These results imply that acid-catalysed cleavage ofpyrryl group in the reaction increases on increasing theconcentration of reactant and the template effect of trihalo-genated acid (TFA and BF3–etharate) assists the formation ofhexaphyrinogen. The template effect of trihalogenated acid inthe cyclization reactions, have been previously reported withdipyrromethane and acetone.17 Similar concentration studieswere carried out with selenophene diol (3h) and dipyrrane (4h)to get 5h, 6h, 7h and 8h. The yield of these reactions did not varymuch in comparison to tellurophene condensation reactions asreported above.

The structures of all the products were characterized by IR,1H NMR, 13C NMR, CHN analysis andmass spectrometry (ESI†).In the 1H NMR spectra of 5a, 5c and 5g in CDCl3, telluropheneprotons are more deshielded and appeared at d 7.24–7.14 ppmcompared to the selenophene protons (d 6.84–6.82 ppm) of 5b,5d and 5h due to better acceptor ability of s*(Te–carbon) bondof tellurium than selenium.11a In the 125Te NMR (ESI†), chem-ical shi values of porphyrinogens 5a, 5c and 5g were appearedas singlet at d 758.91, 755.08 and 754.88 ppm respectively. Thesevalues are more similar to the 125Te chemical shi for tellur-ophene (d 775.1 ppm).18 While in case of 77Se NMR of por-phyrinogen 5b, 5d and 5h, it showed upeld as compared tocorresponding tellurophene porphyrinogens and exhibited 77SeNMR signal at d 601.02, 596.16 and 593.75 ppm respectively.Suitable crystal of 5g for single-crystal X-ray diffraction wasobtained as shown in Fig. 2.19 The analysis of the above resultrevealed that 5g adopt an 1,3-alternate conformation in thesolid state. Porphyrinogen 5g has a Te/Te distance of 4.61 �Aand the two Te atoms occupy the same side of core and noipped tellurophene was found in the crystal.12c

The electronic absorption spectroscopic titration of5,10,15,20-meso-octamethyl-21,23-ditelluraporphyrinogen (5g)with “so” Lewis acid, mercuric perchlorate Hg(ClO4)2 wereperformed in dry acetonitrile at room temperature. Porphyri-nogen 5g gives a characteristic absorption maxima at 284 nm,

Fig. 2 X-ray crystal structure of 5g (ORTEP plot).

This journal is © The Royal Society of Chemistry 2014

Fig. 3 The absorption spectra of 5g (4.2 � 10�6) in acetonitrile uponthe addition of 20 mL stock solution (4.2 � 10�6) of mercuricperchlorate.

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on the addition of Hg2+ in to acetonitrile solution of5g (1 : 1 complex), the absorption peak was bathochromicallyshied to 296 nm with the increase in relative intensity (Fig. 3).The binding constant Ka of 5g–Hg2+ complex was found to be1.45 � 105 M�1. The method of continuous variation (Job's plot)was also used to prove the 1 : 1 stoichiometry (ESI†). Acomparative study for the binding of Hg2+ cation with por-phyrinogen 5g and 5,10,15,20-meso-octamethyl-21,23-dithia-porphyrinogen (N2S2) was performed and it was observed thatporphyrinogen 5g showed more bathochromic shi (12 nm)than 5,10,15,20-meso-octamethyl-21,23-dithiaporphyrinogen(3 nm). The electronic absorption spectroscopic titration ofHg2+ with 7g and 8g were also performed and their respectivepreliminary peaks were shied by 10–12 nm. UV-Vis spectra of7g and 8g with Hg2+ are given in ESI.†

The 1H NMR data of Hg2+ with tellurium and seleniumporphyrinogen at 298 K are reported in Table 2. A signicantdowneld chemical shi change was observed for tellur-ophene and selenophene protons of 5g and 5h, whichsuggests that the interaction takes place through the tellu-rium and selenium donor atom of the tellurophene andselenophene rings. Furthermore, the involvement of telluriumof tellurophene and selenium of selenophene in binding withHg2+ ion, was conrmed by 125Te and 77Se NMR. The 5gexhibited a signal at 754.88 ppm in 125Te NMR which wassignicantly downeld shied by 1.21 ppm and appeared at

Table 2 Changes in the 1H, 125Te and 77Se NMR chemical shifts (d in pp

Porphyrinogen

1H

HMethyl HPyrrole

5g 1.63 5.815g + Hg2+ �0.03 +0.115h 1.61 5.855h + Hg2+ �0.02 +0.09Calix[4]pyrrole 1.51 5.91Calix[4]pyrrole + Hg2+ �0.04 +0.02

This journal is © The Royal Society of Chemistry 2014

756.09 ppm (ESI†). Similarly selenium of porphyrinogen 5h inthe 77Se NMR showed downeld shi by 0.71 ppm in thepresence of Hg2+. The calix[4]pyrrole was also investigated forits interaction with the Hg2+ cation at 298 K and no signicantchemical shi change was observed for the NH of calix[4]-pyrrole, suggesting the absence of complexation betweenpyrrolic ligand and Hg2+ cation. It indicates the incapability ofthe NH groups of the pyrrolic units to bind with the Hg2+

cation.

Conclusion

In summary, the selenium and tellurium N2Te2, N2Se2, N3Teand N3Se meso-unsubstituted core-modied porphyrinogensand N2Te2, N2Se2, N2TeSe meso-substituted core-modied por-phyrinogens have been synthesized for the rst time. The meso-unsubstituted porphyrinogens are oxidized by chloranil tocorresponding porphyrins and porphines which are easilyreduced to chlorin and bacteriochlorin. The meso-substitutedporphyrinogens are used for the complexation of Hg2+ ion. Thereaction approach using readily available conjugated diynes asstarting materials make this strategy highly attractive in diver-sity oriented synthesis.

Experimental sectionGeneral

Melting points were determined on a capillary melting pointapparatus and are uncorrected. The 1H NMR and 13C NMRspectra were recorded on Jeol (400 MHz, 75MHz) spectrometersat room temperature using TMS as an internal standard. Thechemical shis (d ppm) are referenced to the respective solventsand splitting patterns are designed as s (singlet), d (doublet), t(triplet), m (multiplet), dt (double triplet), br (broad) and brs(broad singlet). The 77Se NMR and 125Te NMR spectra wererecorded on a DPX-300 Bruker spectrometer at 57.24 and94.69 MHz and the chemical shis were reported relative toMe2

77Se and Me2125Te. The mass spectra of selected

compounds were recorded on Agilent tech. high resolution Q-TOF mass spectrometry. The column chromatography wascarried out using silica gel (100–200 mesh). Solvents used wereof analytical grade and were dried before use. Pyrrole wasdistilled before use. All other chemicals were purchased inreagent quality and were used as received. All processes andreactions were carried out under argon and protected from

m) for 5g, 5h and calix[4]pyrrole complexes in CDCl3 at 298 K

125Te 77SeHTelluro/Seleno HNH

7.24 7.26 754.88 —+0.31 +0.11 +1.21 —6.83 7.19 — 593.75+0.24 +0.09 — +0.71— 7.06 — —— +0.06 — —

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light. 2,5-Bis(hydroxymethyl)pyrrole and 2,5-bis(2-pyrrolyl-methyl)pyrrole were prepared according to the literaturemethod.2a

Synthesis of diynediols (2a–d). The diynediols (2a–d) weresynthesized by slightly modifying the literature procedure.17 Thesolution of TMEDA (0.4mmol), CuI (0.1 mmol), and NiCl2$6H2O(0.1 mmol) in THF (5 mL) was stirred at room temperature.Terminal alkynes (1a–d) (2 mmol) were dissolved in THF (5 mL)and added slowly with the bubbling of oxygen in the solution.The reaction was monitored by TLC. Aer completion of thereaction (1 h), the mixture was concentrated under reducedpressure and puried by column chromatography on silica gel.The product was eluted with 20% ethyl acetate in hexane to givediynediol as pale yellow solid (93–89%).

Hexa-2,4-diyne-1,6-diol (2a). White solid (92%), mp 112 �C;1H NMR (400 MHz, DMSO): d ¼ 4.31 (s, 4H, CH2), 2.11 (s, 2H,OH); 13C NMR (75 MHz, DMSO): d ¼ 78.11, 70.21, 49.3; HRQ-TOFMS,m/z 111.09 (M + 1) (calcd for C6H6O2 110.03); analysis:calcd for C6H6O2 C, 65.45; H, 5.49; found: C, 65.25; H, 5.16%.

Octa-3,5-diyne-2,7-diol (2b).White solid (97%), mp 94–96 �C;1H NMR (400 MHz, CDCl3): d ¼ 4.57–4.54 (q, 2H, CH), 2.15 (s,2H, OH), 1.45–1.44 (d, 6H, CH3);

13C NMR (75 MHz, CDCl3): d ¼79.4, 65.1, 59.4, 20.9; HR Q-TOFMS,m/z 139.09 (M + 1) (calcd forC8H10O2 138.06); analysis: calcd for C8H10O2 C, 69.54; H, 7.30;found: C, 70.24; H, 7.21%.

1,6-Diphenyl-hexa-2,4-diyne-1,6-diol (2c). White solid (92%),mp 102 �C (lit. mp 102);12c 1H NMR (CDCl3, 400 MHz): d ¼ 7.50–7.30 (m, 10H, Ar-H), 5.50 (s, 2H, CH), 2.13 (br, 2H; OH); 13C NMR(CDCl3, 75 MHz): d ¼ 139.75, 129.17, 127.50, 127.01, 80.35,70.90, 65.35; HR Q-TOF MS, m/z 263.09 (M + 1) (calcd forC18H14O2 262.09); analysis: calcd for C6H6O2 C, 82.42; H, 5.38;found C, 83.01; H, 5.01%.

2,7-Dimethylocta-3,5-diyne-2,7-diol (2d). White solid (93%),mp 134 �C; 1H NMR (400MHz, CDCl3): d¼ 1.98 (s, 2H, OH), 1.52(s, 12H, CH3);

13C NMR (75MHz, CDCl3): d¼ 83.89, 66.33, 65.93,30.96; IR (KBr) nmax 3221, 2982, 2935, 1449, 1381, 1364, 1210,1170, 954, 889, 731, 553; HR Q-TOF MS, m/z 167.089 (M + 1)(calcd for C10H14O2 166.099); analysis: calcd for C10H14O2 C,72.26; H, 8.49; found: C, 72.02; H, 8.19%.

Synthesis of tellurophene and selenophene diols (3a–h). A250mL three-necked ask equipped with a nitrogen inlet, reuxcondenser and dropping funnel was loaded with tellurium/selenium (4 mmol), NaBH4 (16 mmol), and distilled water(10 mL). The mixture was vigorously stirred under nitrogen for30 min. A deoxygenated solution of diynediol (2a–d) (3.1 mmol)in MeOH (12 mL) with AgOAc (50 mg) was added drop wise andthe mixture was stirred overnight. Aer completion of thereaction, water (100 mL) was added and the product wasextracted with benzene–diethylether (1 : 1, 150 mL). Theorganic layer was washed with water (2 � 20 mL), dried overNa2SO4 and evaporated under reduced pressure to give (3a–h) asa off white solid (86–91%).

2,5-Bis(hydroxymethyl)tellurophene (3a). Off white solid(85%), mp 106 �C (lit. mp 106–107 �C);20a 1H NMR (CDCl3, 400MHz): d ¼ 7.35 (s, 2H, tellurophene), 4.77 (s, 4H, CH2), 2.02 (s,2H, OH); 13C NMR (75 MHz, CDCl3): d ¼ 158.6, 130.35, 64.97;HR Q-TOF MS, m/z 243.12 (M + 1) (calcd for C6H8O2Te 241.95);

3176 | RSC Adv., 2014, 4, 3171–3180

analysis: calcd for C6H8O2Te C, 30.06; H, 3.36; found C, 30.36;H, 3.61%.

2,5-Bis(hydroxymethyl)selenophene (3b). Light yellow solid(82%), mp 119 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 6.98 (s, 2H,selenophene), 4.79 (s, 4H, CH2), 2.06 (brs, 2H, OH); 13C NMR(75 MHz, CDCl3): d ¼ 151.6, 126.5, 62.5; HR Q-TOF MS, m/z193.55 (M + 1) (calcd for C6H8O2Se 191.96); analysis: calcd forC6H8O2Se C, 37.71; H, 4.22; found C, 38.11; H, 4.47%.

2,5-Bis(hydroxy(methyl)methyl)tellurophene (3c). Whitesolid (87%), mp 98 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 7.31(s, 2H, tellurophene), 4.89–4.87 (m, 2H, CH), 2.24 (s, 2H, OH),1.49 (s, 6H, CH3);

13C NMR (75 MHz, CDCl3): d ¼ 157.4, 131.2,71.2, 27.2; HR Q-TOF MS, m/z 271.08 (M + 1) (calcd forC8H12O2Te 269.99); analysis: calcd for C8H12O2Te C, 35.88; H,4.52; found C, 35.30; H, 4.33%.

2,5-Bis(hydroxy(methyl)methyl)selenophene (3d). Whitesolid (83%), mp 109 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 6.86 (s,2H, selenophene), 4.94–4.92 (m, 2H, CH), 3.48 (s, 2H, OH), 1.47–1.45 (s, 6H, CH3);

13C NMR (75 MHz, CDCl3): d ¼ 156.5, 124.2,124.1, 67.9, 25.8, 25.7; HR Q-TOF MS, m/z 221.01 (M + 1) (calcdfor C8H12O2Se 220.00); analysis: calcd for C8H12O2Se C, 43.85;H, 5.52; found C, 43.95; H, 5.10%.

2,5-Bis(hydroxy(phenyl)methyl)tellurophene (3e). Whitesolid (86%), mp 146 �C (lit. mp 145–146 �C);12c 1H NMR (CD3OD,400 MHz): d ¼ 7.36–7.23 (m, 10H, Ar-H), 7.23 (s, 2H, tellur-ophene), 5.68 (s, 2H, CH); 13C NMR (CD3OD, 75MHz): d¼ 156.4,141.7, 136.3, 131.3, 126.5, 128.3, 76.5; IR (KBr) nmax 3403, 2925,1626, 1111, 1005, 812, 775, 700; HR Q-TOF MS, m/z 395.02 (M +1) (calcd for C18H16O2Te 394.02); analysis: calcd for C18H16O2TeC, 55.16; H, 4.11; found C, 55.46; H, 4.30%.

2,5-Bis(hydroxy(phenyl)methyl)selenophene (3f). Whitesolid (83%), mp 136 �C (lit. mp 136–137 �C);20b 1H NMR (CD3OD,400 MHz): d ¼ 7.35–7.21 (m, 10H, Ar-H), 6.81 (s, 2H, seleno-phene), 5.69 (s, 2H, CH); 13C NMR (CD3OD, 75 MHz): d ¼ 157.4,143.7, 139.3, 129.3, 128.5, 126.3, 73.5; IR (KBr) nmax 3378, 1492,1452, 1394, 1282, 1255, 1121, 998, 835, 815, 780, 725, 699, 610,497; HR Q-TOF MS, m/z 345.12 (M + 1) (calcd for C18H16O2Se344.03); analysis: calcd for C18H16O2Se C, 62.98; H, 4.70; foundC, 62.36; H, 4.51%.

2,5-Bis(hydroxy(dimethyl)methyl)tellurophene (3g). Whitesolid (88%), mp 95 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 7.24 (s,2H, tellurophene), 2.17 (s, 2H, OH), 1.58 (s, 12H); 13C NMR(75 MHz, CDCl3): d ¼ 161.74, 130.35, 74.97, 32.25; IR (KBr) nmax

3326, 2970, 2924, 1497, 1458, 1373, 1360, 1244, 1207, 1147,1094, 933, 811, 799, 663, 552; HR Q-TOF MS, m/z 299.01 (M + 1)(calcd for C10H16O2Te 298.02); analysis: calcd for C10H16O2Te C,40.60; H, 5.45; found C, 40.20; H, 5.15%.

2,5-Bis(hydroxy(dimethyl)methyl)selenophene (3h). Offwhite solid (81%), mp 114 �C; 1H NMR (CDCl3, 400 MHz): d ¼6.89 (s, 2H, selenophene), 2.15 (s, 2H, OH), 1.63 (s, 12H); 13CNMR (75 MHz, CDCl3): d¼ 160.55, 123.23, 72.78, 32.28; IR (KBr)nmax 3307, 2979, 2930, 2867, 1451, 1408, 1357, 1358, 1245, 1167,1153, 1047, 9470, 794, 603; HR Q-TOF MS, m/z 249.03 (M + 1)(calcd for C10H16O2Se 248.03); analysis: calcd for C10H16O2Se C,48.59; H, 6.52; found C, 49.09; H, 6.25%.

Synthesis of dipyrranes (4a–h). Borontriuoride-etherate (0.3mmol) was added to solution of diols (3a–h) (0.6 mmol) in

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degassed pyrrole (6 mL), and the resulting mixture was stirredfor 1 h under argon. The reaction was monitored by TLC. Aercompletion of the reaction, it was diluted with CH2Cl2 (30 mL)and 40% NaOH (25 mL). The organic layer was separated andwashed with water (3 � 100 mL) and brine (100 mL). It wasdried over MgSO4 and concentrated under reduced pressure.The product was puried over silica gel (70 : 30 hexanes–EtOAc)to give (89–94%) of (4a–h) as a light brown solid.

2,5-Bis(2-pyrrolylmethyl)tellurophene (4a). White solid(75%), mp 98 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 7.95 (br, 2H,NH), 7.20 (s, 2H, tellurophene), 6.66 (m, 2H, pyrrol), 6.11–6.03(m, 4H, pyrrol), 4.11 (s, 4H, CH2);

13C NMR (CDCl3, 75 MHz): d¼163.1, 138.3, 129.7, 116.91, 108.7, 103.35, 31.9; IR (KBr) nmax

3367, 2831, 1499, 1379, 1360, 1233, 1236, 991, 1031, 1010, 98,1807, 723; HR Q-TOF MS, m/z 341.11 (M + 1) (calcd forC14H14N2Te 340.02); analysis: calcd for C14H14N2Te C, 49.77; H,4.18; N, 8.29; found C, 49.81; H, 4.15; N, 8.69%.

2,5-Bis(2-pyrrolylmethyl)selenophene (4b). White solid(73%), mp 56 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 7.93 (br, 2H,NH), 6.81 (s, 2H, selenophene), 6.67–6.65 (m, 2H, pyrrol), 6.11–6.03 (m, 4H, pyrrol), 4.12 (s, 4H, CH2);

13C NMR (CDCl3, 75MHz): d ¼ 148.79, 130.1, 126.8, 117.1, 108.4, 106.2, 31.5; HR Q-TOF MS, m/z 291.03 (M + 1) (calcd for C14H14N2Se 290.03);analysis: calcd for C14H14N2Se C, 58.14; H, 4.88; N, 9.69; foundC, 58.52; H, 4.51; N, 9.38%.

2,5-Bis(2-pyrrolyl(methyl)methyl)tellurophene (4c). Brownoil (91%); 1H NMR (CDCl3, 400 MHz): d¼ 7.86 (br, 2H, NH), 7.15(m, 2H, tellurophene), 6.58–6.57 (m, 2H, pyrrol), 6.06–6.03 (m,2H, pyrrol), 5.95 (m, 2H, pyrrol), 4.13–4.08 (m, 2H, CH), 1.54–1.51 (m, 6H, CH3);

13C NMR (CDCl3, 75 MHz): d ¼ 162.41,140.73, 131.27, 116.91, 107.71, 103.35, 42.04, 31.92; HR Q-TOFMS, m/z 367.10 (M + 1) (calcd for C16H18N2Te 368.05); analysis:calcd for C16H18N2Te C, 52.52; H, 4.96; N, 7.66; N, 7.11; found C,52.86; H, 4.91; N, 7.21%.

2,5-Bis(2-pyrrolyl(methyl)methyl)selenophene (4d). Lightbrown oil (88%); 1H NMR (CDCl3, 400 MHz): d ¼ 7.86 (br, 2H,NH), 7.15 (m, 2H, tellurophene), 6.58–6.57 (m, 2H, pyrrol), 6.06–6.03(m, 2H, pyrrol), 5.95 (m, 2H, pyrrol), 4.13–4.08 (m, 2H, CH),1.54–1.51(m, 6H, CH3);

13C NMR (CDCl3, 75 MHz): d ¼ 171.2,155.6, 135.2, 125.0, 117.6, 116.8, 108.0, 104.3, 60.3, 36.4, 23.14,21.0, 14.1; HR Q-TOF MS, m/z 319.32 (M + 1) (calcd forC16H18N2Se 318.06); analysis: calcd for C16H18N2Se C, 60.57; H,5.72; N, 8.83; found C, 59.91; H, 5.12; N, 8.53%.

2,5-Bis(2-pyrrolyl(phenyl)methyl)tellurophene (4e). Lightbrown oil (85%); 1H NMR (CDCl3, 400 MHz): d ¼ 7.95 (br, 2H,NH), 7.30 (m, 10H, Ar-H), 7.24 (s, 2H, tellurophene), 6.65 (br,2H, pyrrol), 6.10 (m, 2H, pyrrol), 5.96 (m, 2H, pyrrol), 5.46 (m,2H, CH); 13C NMR (CDCl3, 75 MHz): d ¼ 154.3, 144.5, 134.8,134.4, 138.6, 128.2, 127.0, 117.0, 108.3, 107.1, 50.9; HR Q-TOFMS, m/z 493.26 (M + 1) (calcd for C26H22N2Te 492.08); analysis:calcd for C26H22N2Te C, 63.72; H, 4.52; N, 5.72; found C, 63.92;H, 4.65; N, 5.42%.

2,5-Bis(2-pyrrolyl(phenyl)methyl)selenophene (4f). Brown oil(83%); 1H NMR (CDCl3, 400 MHz): d ¼ 7.95 (br, 2H, NH), 7.30(m, 10H, Ar-H), 7.24 (s, 2H, selenophene), 6.65 (br, 2H, pyrrol),6.10 (m, 2H, pyrrol), 5.96 (m, 2H, pyrrol), 5.46 (m, 2H, CH); 13CNMR (CDCl3, 75 MHz): d ¼ 156.2, 143.8, 133.9, 134.8, 139.1,

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127.5, 126.9, 117.5, 107.8, 107.3, 50.5; HR Q-TOF MS,m/z 443.26(M + 1) (calcd for C26H22N2Se 442.09); analysis: calcd forC26H22N2Se C, 70.74; H, 5.02; N, 6.35; found C, 70.36; H, 5.13; N,6.65%.

2,5-Bis(2-pyrrolyl(dimethyl)methyl)tellurophene (4g). Whitesolid (93%), mp 148 �C; 1H NMR (CDCl3, 400 MHz): d¼ 7.93 (br,2H, NH), 7.10 (s, 2H, tellurophene), 6.65 (m, 2H, pyrrol), 6.10–6.03 (m, 4H, pyrrol), 1.66 (s, 12H, CH3);

13C NMR (CDCl3, 75MHz): d ¼ 162.41, 140.73, 131.27, 116.91, 107.71, 103.35, 42.04,31.92; IR (KBr) nmax 3367, 2964, 2861, 1559, 1381, 1361, 1254,1236, 1112, 1037, 1010, 965, 807, 723, 581; HR Q-TOF MS, m/z397.08 (M + 1) (calcd for C18H22N2Te 396.08); analysis: calcd forC18H22N2Te C, 54.87; H, 5.63; N, 7.11; found C, 54.30; H, 5.93; N,7.41%.

2,5-Bis(2-pyrrolyl(dimethyl)methyl)selenophene (4h). Whitesolid (91%), mp 97 �C; 1H NMR (CDCl3, 400 MHz): d ¼ 7.91 (br,2H, NH), 6.71 (s, 2H, selenophene), 6.65 (m, 2H, pyrrol), 6.12–6.05 (m, 4H, pyrrol), 1.69 (s, 12H, CH3);

13C NMR (CDCl3, 75MHz): d ¼ 160.94, 139.68, 124.10, 116.78, 107.72, 103.54, 39.68,31.61; IR (KBr) nmax 3372, 3099, 2967, 1559, 1439, 1383, 1312,1296, 1231, 1112, 1036, 949, 803, 722, 583; HR Q-TOF MS, m/z347.11 (M + 1) (calcd for C18H22N2Se 346.09); analysis: calcd forC18H22N2Se C, 62.60; H, 6.42; N, 8.11; found C, 62.56; H, 6.22; N,8.51%.

Synthesis of porphyrinogens (5a–i)

Synthesis of porphyrinogens 5a–d (method A). To a degassedsolution of dipyrranes (4a–d) (2 mmol) in CH2Cl2 (200 mL), themethanolic solution (5 mL) of corresponding diols (3a–d)(2 mmol) were added. The reaction was carried out at 0 �C in adark room under argon. Aer 20 min, 20% BF3$CH3OH solution(0.4 mmol) was added with a micropipette and the reactionmixture was stirred for 1 h. Further stirring for 1 h wascontinued at room temperature. Aer completion of the reac-tion, the solvent was evaporated under reduced pressure to giveviscous colorless oil. The viscous oil was puried by columnchromatography on silica gel using CH2Cl2 as an eluent toafford a colorless solid 5a–d (15–27%).

Synthesis of porphyrinogens 5g–i (method B). To a degassedsolution of 4g–h (0.5 mmol) and corresponding diol 3g–h (0.50mmol) in CH2Cl2 (250 mL), BF3$OEt2 (0.091 mmol) was addedand the reaction mixture was stirred for 1 h at room tempera-ture. The reaction was monitored by TLC. Aer completion ofthe reaction, a saturated aqueous Na2CO3 solution (200 mL)was poured into the reaction mixture. The organic phase wasseparated and washed with aqueous Na2CO3 (3 � 100 mL) andbrine (200 mL). It was dried over Na2SO4 and evaporated underreduced pressure. The residue was subjected to silica gelcolumn chromatography (hexane–CH2Cl2 ¼ 3/2). The (Rf 0.5)was collected and evaporated to afford 5g–i as a white solid(39–43%).

5,10,15,20-Meso-octahydro-21,23-ditelluraporphyrinogen (5a).White solid (15%); mp 171 �C (decompose); 1H NMR (CDCl3, 400MHz): d ¼ 7.34 (br, 2H, NH), 7.14 (s, 4H, tellurophene), 5.71–5.55(d, J ¼ 2.2 Hz, 4H, pyrrol), 3.92 (s, 8H, CH2);

13C NMR (CDCl3,75 MHz): d ¼ 150.6, 130.9, 130.0, 105.2, 31.5; 125Te NMR (CDCl3):

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d ¼ 758.91 (s); IR (KBr) nmax 3412, 2991, 2923, 2841, 1598, 1481,1451, 1416, 1267, 1222, 1101, 1045, 987, 784, 771, 720; HR Q-TOFMS,m/z 546.961 (M + 1) (calcd for C20H18N2Te2 545.959); analysis:calcd for C20H18N2Te2 C, 44.36; H, 3.35; N, 5.17; found: C, 44.56;H, 3.41; N, 5.19%.

5,10,15,20-Meso-octahydro-21,23-diselenaporphyrinogen (5b).Off white solid (11%); mp 162 �C (decompose); 1H NMR (CDCl3,400 MHz): d ¼ 7.38 (br, 2H, NH), 6.82 (s, 4H, selenophene), 5.87–5.86 (d, J¼ 2.2 Hz, 4H, pyrrol), 4.04 (s, 8H, CH2);

13C NMR (CDCl3,75MHz): d¼ 150.4, 130.8, 126.5, 105.6, 31.6; 77Se NMR (CDCl3): d¼ 601.02 (s); IR (KBr) nmax 3444, 2915, 1642, 1420, 1381, 1230,1049, 799, 741, 715, 581; HRQ-TOFMS,m/z 446.981 (M + 1) (calcdfor C20H18N2Se2 445.980); analysis: calcd for C20H18N2Se2 C,54.07; H, 4.08; N, 6.31; found: 53.93; H, 4.09; N, 6.22%.

5,10,15,20-Meso-tetramethyl-21,23-ditelluraporphyrinogen(5c). Light brown solid (27%), mp 130 �C (decompose); 1HNMR (CDCl3, 400 MHz): d ¼ 7.33 (br, 2H, NH, stereoisomer A),7.35 (br, 2H, NH, stereoisomer B), 7.38 (br, 2H, NH, stereo-isomer C), 7.24 (s, 4H, tellurophene, stereoisomer A), 7.25 (s,4H, tellurophene, stereoisomer B), 7.29 (s, 4H, tellurophene,stereoisomer C), 5.83 (s, 4H, pyrrol, stereoisomer A), 5.86 (s,4H, pyrrol, stereoisomer B), 5.87 (s, 4H, pyrrol, stereoisomerC), 4.02–3.97 (m, 4H, CH, stereoisomer A), 4.14–4.11 (m, 4H,CH, stereoisomer B), 4.14–4.11 (m, 4H, CH, stereoisomer C),1.54 (s, 12H, CH3, stereoisomer A), 1.56–1.58 (s, 12H, CH3,stereoisomer B), 1.58 (s, 12H, CH3, stereoisomer C); 13C NMR(CDCl3, 75 MHz): d ¼ 158.7, 158.6, 157.1, 156.7, 154.7, 137.3,137.2, 137.1, 131.8, 131.7, 131.6, 102.5, 102.4, 102.3, 40.5,40.3, 39.9, 23.6, 23.5, 23.4; 125Te NMR (CDCl3): d ¼ 755.08 (s);HR Q-TOF MS, m/z 603.025 (M + 1) (calcd for C24H26N2Te2602.022); analysis: calcd for C24H26N2Te2 C, 48.23; H, 4.38; N,4.69; found: C, 48.44; H, 4.59; N, 4.93%.

5,10,15,20-Meso-tetramethyl-21,23-diselenaporphyrinogen(5d). Off white solid (22%), mp 186 �C (decompose); 1H NMR(CDCl3, 400 MHz): d ¼ 7.26 (br, 2H, NH, stereoisomer A), 7.29(br, 2H, NH, stereoisomer B), 7.29 (br, 2H, NH, stereoisomer C),6.82 (s, 4H, selenophene, stereoisomer A), 6.85–6.84 (m, 4H,selenophene, stereoisomer B), 6.86–6.87 (m, 4H, selenophene,stereoisomer C), 5.86 (m, 4H, pyrrol, stereoisomer A), 5.87 (m,4H, pyrrol, stereoisomer B), 5.89 (m, 4H, pyrrol, stereoisomerC), 4.17 (m, 4H, CH, stereoisomer A), 4.19 (m, 4H, CH, stereo-isomer B), 4.20 (m, 4H, CH, stereoisomer C), 1.54 (s, 12H, CH3,stereoisomer A), 1.55 (s, 12H, CH3, stereoisomer B), 1.57 (s, 12H,CH3, stereoisomer C); 13C NMR (CDCl3, 75 MHz): d ¼ 157.5,157.3, 156.4, 155.3, 136.2, 136.1, 124.6, 124.4, 103.6, 103.2,103.1, 37.0, 36.9, 36.5, 22.5, 22.3, 22.2; 77Se NMR (CDCl3): d ¼596.16 (s); HR Q-TOF MS, m/z 503.045 (M + 1) (calcd forC24H26N2Se2 502.042); analysis: calcd for C24H26N2Se2 C, 57.61;H, 5.24; N, 5.60; found: C, 57.81; H, 5.32; N, 5.55%.

5,10,15,20-Meso-octamethyl-21,23-ditelluraporphyrinogen(5g). White solid (41%), mp 226 �C; 1H NMR (CDCl3, 400 MHz):d ¼ 7.27 (br, 2H, NH), 7.24 (s, 4H, tellurophene), 5.81–5.80 (d,J ¼ 2.4 Hz, 4H, pyrrol), 1.63 (s, 24H, CH3);

13C NMR (CDCl3, 75MHz): d ¼ 163.64, 141.98, 130.02, 101.00, 42.22, 30.79; 125TeNMR (CDCl3): d ¼ 754.88 (s); IR (KBr) nmax 3439, 2960, 2923,2860, 1640, 1495, 1458, 1413, 1247, 1229, 1104, 1039, 997, 794,769, 722, 700, 587, 520; HR Q-TOF MS, m/z 659.0894 (M + 1)

3178 | RSC Adv., 2014, 4, 3171–3180

(calcd for C28H34N2Te2 658.084); analysis: calcd for C28H34N2Te2C, 51.44; H, 5.24; N, 4.28; found: C, 51.41; H, 5.19; N, 4.23%.

Synthesis of N-confused cyclic tetramer (6g), cyclic hexamer(7g) and cyclic octamer (8g). The solution of the 2,5-bis(hy-droxymethylethyl)tellurophene (3g) (113 mg, 0.381 mmol) and2,5-bis(pyrrolylmethylethyl)tellurophene (4g) (151 mg, 0.381mmol) in acetonitrile (20 mL, 40 mM concentration) was stirredunder N2 at 0 �C for 15 min and then BF3$OEt2 (0.076 mmol)was added. The reaction was monitored by TLC. Aer 30 min, itwas diluted with CH2Cl2 (100 mL) and washed with aqueousNaOH (0.1 N, 10 mL) and water (2 � 10 mL). The organic layerwas dried over NaHCO3 and concentrated under reducedpressure. The products were separated on column chromatog-raphy (hexane–CH2Cl2 1 : 1) to afford two products, (5g) and(6g). N-confused cyclic tetramer (6g): white solid 7% yield, mp229 �C (decompose); Rf: 0.81 (hexane–CH2Cl2 1 : 1); 1H NMR(CDCl3, 400 MHz): d ¼ 7.69 (br, 1H, NH), 7.49 (br, 1H, NH),7.20–7.16 (m, 4H, tellurophene), 6.37 (s, 1H, pyrrol), 5.78 (m,2H, pyrrol), 5.61 (s, 1H, pyrrol), 1.63–1.61 (m, 24H, CH3);

13CNMR (CDCl3, 75 MHz): d ¼ 163.6, 161.9, 141.9, 139.6, 131.8,130.0, 103.0, 101.0, 42.2, 32.5, 30.8, 29.6; 125Te NMR (CDCl3): d¼ 753.11 (s); IR (KBr) nmax 3436, 3331 2959, 2928, 2854, 1638,1490, 1449, 1420, 1254, 1221, 1121, 1038, 996, 780, 760, 714,701, 583, 521; HR Q-TOF MS, m/z 659.114 (M + 1) (calcd forC28H34N2Te2 658.0846); analysis: calcd for C28H34N2Te2 C,51.44; H, 5.24; N, 4.28; found: C, 51.41; H, 5.19; N, 4.23. Hex-amer (7g): white solid 15% yield, mp 231 �C (decompose); Rf:0.65 (hexane–CH2Cl2 1 : 1); 1H NMR (CDCl3, 400 MHz): d¼ 7.69(br, NH), 6.95 (s, 6H, tellurophene), 5.94–5.93 (d, J ¼ 2.24 Hz,6H, pyrrol), 1.59 (s, 36H, CH3);

13C NMR (CDCl3, 75 MHz): d ¼162.8, 141.5, 129.4, 99.8, 42.8, 31.5; 125Te NMR (CDCl3): d ¼754.65 (s); IR (KBr) nmax 3436, 2954, 2914, 2878, 1649, 1485,1428, 1421, 1230, 1228, 1104, 1025; HR Q-TOF MS, m/z 987.11(M+) (calcd for C42H51N3Te3 987.12); analysis: calcd forC42H51N3Te3 C, 51.44; H, 5.24; N, 4.28; found: C, 51.33; H, 5.19;N, 4.52%. Octamer (8g): white solid 8% yield, mp 223 �C(decompose); Rf: 0.54 (hexane–CH2Cl2 1 : 1); 1H NMR (CDCl3,400 MHz): d¼ 7.64 (br, NH), 6.98 (s, 8H, tellurophene), 5.88 (d, J¼ 2.9, 8H, pyrrol), 1.57 (s, 48H, CH3);

13C NMR (CDCl3, 75 MHz):d ¼ 163.0, 142.4, 129.6, 101.0, 42.5, 30.1; 125Te NMR (CDCl3): d¼ 754.11 (s); IR (KBr) nmax 3435, 2944, 2985, 2756, 1652, 1478,1436, 1391, 1241, 1254, 1110, 995, 780; HR Q-TOF MS, m/z1316.32 (M+) (calcd for C56H68N4Te4 1316.169); analysis: calcdfor C56H68N4Te4 C, 51.44; H, 5.24; N, 4.28; found: C, 51.61; H,5.29; N, 4.46%.

5,10,15,20-Meso-octamethyl-21,23-diselenaporphyrinogen(5h). White solid (39%); mp 198 �C; 1H NMR (CDCl3, 400 MHz):d ¼ 7.19 (br, 2H, NH), 6.83 (s, 4H, selenophene), 5.85–5.84 (d,J ¼ 2.4 Hz, 4H, pyrrol), 1.61 (s, 24H, CH3);

13C NMR (CDCl3, 75MHz): d ¼ 162.64, 143.89, 131.02, 102.00, 41.22, 32.79; IR (KBr)nmax 3444, 2967, 2925, 1630, 1412, 1359, 1235, 1041, 798, 762,725, 596; 77Se NMR (CDCl3): d ¼ 593.75 (s); HR Q-TOF MS, m/z559.108 (M + 1) (calcd for C28H34N2Se2 558.105); analysis: calcdfor C28H34N2Se2 C, 60.43; H, 6.16; N, 5.03; found: C, 60.51; H,6.29; N, 5.01%.

5,10,15,20-Meso-octamethyl-21-tellura-23-selenaporphyri-nogen (5i). Off white solid (43%); mp 241 �C; 1H NMR (CDCl3,

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400 MHz): d ¼ 7.27 (br, 2H, NH), 7.24 (s, 2H, tellurophene), 6.91(s, 2H, selenophene) 5.89–5.85 (dt, 4H, pyrrol), 1.687–1.671 (d,J ¼ 6.4, 24H, CH3);

13C NMR (CDCl3, 75 MHz): d ¼ 164.34,161.73, 142.32, 140.82, 129.47, 122.80, 101.59, 101.10, 42.20,39.66 30.73, 30.35; 125Te NMR (CDCl3): d ¼ 753.96 (s); 77Se NMR(CDCl3): d ¼ 594.02 (s); IR (KBr) nmax 3447, 2927, 2865, 1607,1431, 1359, 1233, 1040, 799, 763, 593, 512; HR Q-TOF MS, m/z609.093 (M + 1) (calcd for C28H34N2SeTe 608.09); analysis: calcdfor C28H34N2SeTe C, 55.57; H, 5.66; N, 4.63; found: C, 55.68; H,5.71; N, 4.49%.

5,10,15,20-Meso-octahydro-21-telluraporphyrinogen (9a).Synthesized by method A; white solid (7%); mp 158 �C(decompose); 1H NMR (CDCl3, 400 MHz): d ¼ 7.88 (br, 2H,NH), 7.58 (br, 1H, NH), 7.18 (s, 2H, tellurophene), 5.95 (s, 2H,pyrrol), 5.84–5.77 (m, 4H, pyrrol), 3.99 (s, 4H, CH2), 3.86 (s,4H, CH2);

13C NMR (CDCl3, 75 MHz): d ¼ 150.5, 130.8, 130.1,129.9, 105.6, 104.9, 103.9, 31.8, 30.6; 125Te NMR (CDCl3): d ¼761.33 (s); IR (KBr) nmax 3351, 3329, 1589, 1188, 1129, 1078,1026, 1007, 768, 765, 759, 748, 706, 569; HR Q-TOF MS, m/z431.081 (M+) (calcd for C20H19N3Te 431.064); analysis: calcdfor C20H19N3Te C, 56.00; H, 4.46; N, 9.80; found: C, 56.11; H,4.35; N, 9.73%.

5,10,15,20-Meso-octahydro-21-telluraporphyrinogen (N-confused) (9b). Synthesized by method A; white solid (8%); mp161 �C (decompose); 1H NMR (CDCl3, 400 MHz): d ¼ 7.79 (br,1H, NH), 7.60 (br, 1H, NH), 7.41 (br, 1H NH), 7.09–7.08 (m, 1H,tellurophene), 7.00–6.98 (m, 1H, tellurophene), 6.46 (m, 1H,pyrrol), 5.90–5.78 (m, 5H, pyrrol), 3.87 (s, 2H, CH2), 3.86 (s, 2H,CH2), 3.78 (s, 2H, CH2), 3.67 (s, 2H, CH2);

13C NMR (CDCl3, 75MHz): d ¼ 150.7, 150.5, 131.9, 131.2, 130.9, 129.5, 112.0, 105.0,104.2104.1, 103.5, 99.2, 31.6, 30.8, 30.0; 125Te NMR (CDCl3): d ¼759.21 (s); IR (KBr) nmax 3347, 3336, 3128, 3108, 1573, 1181,1125, 1089, 1018, 1008, 799, 764, 751, 742, 711, 558; HR Q-TOFMS, m/z 431.061 (M+) (calcd for C20H19N3Te 431.064); analysis:calcd for C20H19N3Te C, 56.00; H, 4.46; N, 9.80; found: C, 56.15;H, 4.43; N, 9.91%.

5,10,15,20-Meso-octahydro-21-selenaporphyrinogen (10a).Synthesized by method A; white solid (11%), mp 153 �C; 1HNMR (CDCl3, 400 MHz): d¼ 7.88 (br, 2H, NH), 7.54 (br, 1H, NH),6.74 (s, 2H, selenophene), 5.84–5.81 (m, 6H, pyrrol), 4.07 (s, 4H,CH2), 4.92 (s, 4H, CH2);

13C NMR (CDCl3, 75 MHz): d ¼ 150.2,131.6, 130.9, 130.4, 126.3, 105.5, 104.8, 103.1, 31.7, 30.0; 77SeNMR (CDCl3): d ¼ 603.14 (s); IR (KBr) nmax 3341, 3333, 3118,1581, 1192, 1131, 1092, 1020, 1003, 791, 763, 758, 748, 710, 561;HR Q-TOF MS,m/z 381.011 (M+) (calcd for C20H19N3Se 381.072);analysis: calcd for C20H19N3Se C, 63.16; H, 5.04; N, 11.05; found:C, 63.21; H, 4.96; N, 11.01%.

21,23-Diselenaporphine. To a degassed solution of5,10,15,20-meso-octahydro-21,23-diselenaporphyrinogen (5b) (1mmol) in CHCl3 (10 mL), 0.1% aqueous FeCl3 solution wasadded at 0 �C in dark under argon and stirred for 10 min. Theorganic solvent was separated and evaporated under reducedpressure. The crude was puried by column chromatography onsilica gel using CH2Cl2 as an eluent to afford light brown solid of21,23-diselenaporphine; mp 68 �C (decompose); 1H NMR(CDCl3, 400 MHz): d ¼ 10.49 (s, 4H, meso-CH) 10.29 (s, 4H,selenophene), 9.36 (s, 4H, pyrrol); 13C NMR (CDCl3, 75 MHz): d

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¼ 182.7, 158.7, 152.6, 144.8, 108.6; HR Q-TOF MS, m/z 440.976(M + 1) (calcd for C20H12N2Se2 439.933).

5,10,15,20-Meso-tetramethyl-21,23-diselenaporphyrin. To adegassed solution of 5,10,15,20-meso-tetramethyl-21,23-dis-elenaporphyrinogen (5d) (1 mmol) in CHCl3 (10 mL), thep-chloranil (2 mmol) was added at 0 �C in a dark room underargon. Aer 10 min, the solvent was evaporated under reducedpressure to give brown solid. The crude was puried by columnchromatography on silica gel using CH2Cl2 as an eluent toafford a orange solid of 5,10,15,20-meso-tetramethyl-21,23-dis-elenaporphine; mp 173 �C (decompose); 1H NMR (CDCl3, 400MHz): d ¼ 10.15 (s, 4H, selenophene), 9.26 (s, 4H, pyrrol), 4.52(s, 12H, CH3);

13C NMR (CDCl3, 75MHz): d¼ 181.6, 155.7, 152.6,146.4, 134.2, 31.5; 77Se NMR (CDCl3): d ¼ 628.81 (s); HR Q-TOFMS, m/z 497.040 (M + 1) (calcd for C24H20N2Se2 495.996).

Meso-tetramethyldiselenachlorin and meso-tetramethyldi-selenabacteriochlorin. The 5,10,15,20-meso-tetramethyl-21,23-diselenaporphyrin (1 mmol) and anhydrous potassiumcarbonate (10 mmol) were dissolved in dry pyridine and p-tol-uenesulfonhydrazide (2 mmol) in dry pyridine was added. Themixture was heated at 100 �C under argon for 24 hours. Furtherquantities of p-toluenesulfonhydrazide (2 mmol in dry pyri-dine) were added aer 2, 4, 6 and 8 hours. Aer cooling, themixture was treated with ethyl acetate–water (2 : 1) and heatedat 100 �C for 5 min. Aer cooling, the organic phase wasseparated and washed twice with aqueous HCl (2 M), twice withwater then saturated aqueous sodium hydrogen carbonatesolution. Organic layer was concentrated under vacuum. Thecrude product was chromatograph on silica gel eluted with amixture of ethylacetate–hexane (0.1 : 9). Meso-tetramethyldise-lenachlorin: Rf: 0.25 (ETOAc–hexane 0.1 : 9); brown-orangesolid (5%), mp 48 �C (decompose); 1H NMR (CDCl3, 400 MHz):d ¼ 9.64–9.63 (d, J ¼ 4.8, 2H, selenophene), 9.27–9.26 (d, J ¼4.8, 2H, selenophene), 9.07 (s, 2H, pyrrol), 4.61–4.58 (t, 2H,reduced pyrrol), 4.40 (s, 6H, CH3), 4.31–4.27 (t, 2H, reducedpyrrol), 4.01 (s, 6H, CH3);

13C NMR (CDCl3, 75 MHz): d ¼ 181.8,180.7, 161.2, 158.5, 152.4, 143.5, 135.9, 134.7, 127.6, 73.1, 31.0,29.5; HR Q-TOF MS, m/z 499.015 (M + 1) (calcd for C24H22N2Se2498.011). Meso-tetramethyldiselenabacteriochlorin: Rf: 0.20(ETOAc–hexane 0.1 : 9); brown solid (2%), mp 46 �C (decom-pose); 1H NMR (CDCl3, 400 MHz): d ¼ 8.92 (s, 4H, seleno-phene), 4.20 (s, 8H, reduced pyrrol), 3.90 (s, 12H, CH3);

13CNMR (CDCl3, 75 MHz): d ¼ 179.6, 155.7, 143.5128.7, 69.2, 28.1;HR Q-TOF MS, m/z 501.045 (M + 1) (calcd for C24H24N2Se2500.027).

X-ray crystal structure of 5,10,15,20-meso-octamethyl-21,23-ditelluraporphyrinogen (5g). Crystal was grown as colorlessprism by slow evaporation of a benzene solution of 5g layeredwith hexane. C28H34N2Te2, M¼ 658.08 crystal system¼ triclinic;space group ¼ P�1; unit cell dimensions a ¼ 10.361(2) A,b ¼ 11.5721(3) A, c ¼ 11.8258(15) A, alpha ¼ 101.396(15)�,beta ¼ 90.972(13)�, gamma ¼ 104.51(2)�; Z ¼ 2; calculateddensity ¼ 1.613 mg m�3; goodness-of-t on F2 ¼ 0.656; total of13 052 reections were measured, 6096 unique (Rint ¼ 0.0748);nal R indices R ¼ 0.0713, Rw ¼ 0.1865; F(000) ¼ 636; thestructure was rened on full-matrix least-squares on F2.Complete crystallographic data are given in ESI.†

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Acknowledgements

We thank the Department of Science and Technology andUniversity of Delhi, Delhi for nancial assistance. S. Ahmadand K. K. Yadav are thankful to UGC, New Delhi for seniorresearch fellowship and junior research fellowship. S. J. Singhis thankful to UGC, New Delhi for Dr D. S. Kothari Post-doctoralfellowship.

Notes and references

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