www.elsevier.com/locate/poly

Polyhedron 23 (2004) 2193–2202

Synthesis, X-ray and Mossbauer study of iron(II) complexes withtrithiocyanuric acid (ttcH3).

The X-ray structures of [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O and[Fe(phen)3](ttcH2)(ClO4) Æ 2CH3OH Æ 2H2O

Pavel Kopel a,*, Zdenek Travnıcek a, Radek Zboril b, Jaromır Marek c

a Department of Inorganic Chemistry, Palacky University, Krızkovskeho 10, CZ-771 47 Olomouc, Czech Republicb Department of Physical Chemistry, Palacky University, Tr. Svobody 8, CZ-771 46 Olomouc, Czech Republic

c Laboratory of Functional Genomics and Proteomics, Faculty of Sciences, Masaryk University, Kotlarska 2, CZ-611 37 Brno, Czech Republic

Received 26 April 2004; accepted 17 June 2004

Available online 25 August 2004

Abstract

Iron(II) complexes with a combination of nitrogen-donor ligands and trithiocyanuric acid (ttcH3) of the composition

[Fe(bpy)2(ttcH)] Æ 2H2O (1), [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O (2), [Fe(terpyCl)2](ttcH2)2 Æ H2O (3), [Fe(phen)2(ttcH)] Æ 2H2O (4), [Fe-

(nphen)2(ttcH)] Æ 4H2O (5) and [Fe(phen)3](ttcH2)(ClO4) Æ 2CH3OH Æ 2H2O (6), where bpy = 2,2 0-bipyridine, terpyCl = 4 0-chloro-

2,2 0:6 0,2 0-terpyridine, phen = 1,10-phenanthroline, nphen = 5-nitro-1,10-phenanthroline, have been prepared. The compounds,

except for 6, have been characterized by elemental analysis, 57Fe Mossbauer, IR and UV–Vis spectroscopies. It has been found that

the trithiocyanurate ion is either coordinated to the metal centre (1, 4 and 5) or situated outside the inner coordination sphere of the

iron(II) ion (2, 3 and 6). The X-ray crystal structures of complexes 2 and 6 demonstrate that the ligands enforce a distorted octa-

hedral geometry on the FeII ions with monoanionic 2 and dianionic 6 forms of uncoordinated trithiocyanuric acid. Density-func-

tional theory (DFT) calculations (B3LYP/6-31 + G*) were used for the geometry optimisation and infrared frequencies calculations

of differently protonated forms of the acid (ttcH3, ttcH2� and ttcH2�).

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Iron(II) complexes; Trithiocyanuric acid; Mossbauer spectra; Crystal structures; Spectroscopic properties; DFT calculations

1. Introduction

Trithiocyanuric acid (2,4,6-trimercapto-1,3,5-tria-

zine, ttcH3) and its trisodium salt (ttcNa3 Æ 9H2O) are

widely applied in industry, analytical chemistry and bio-chemistry. For example, ttcNa3 Æ 9H2O is used as a pre-

cipitating agent for many heavy metals from

contaminated water [1], as a component of the zinc elec-

0277-5387/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.poly.2004.06.024

* Corresponding author. Tel.: +420 58 563 4354; fax: +420 58 522

5737.

E-mail address: kopel@risc.upol.cz (P. Kopel).

troplating bath, in PVC floor coverings and it may be

also used instead of thiourea in the bleaching of wool

[2–4]. Moreover, it was found that the acid inhibits the

Toxoplasma gondii uracil phosphoribosyltransferase

enzyme in vitro better than 5-fluorouracil andemimycin, i.e. compounds showing an antitoxoplasmal

activity [5,6].

At first, Beezer et al. [7] studied complexes of trithio-

cyanuric acid. The authors found that the formation of

mononuclear, binuclear as well as trinuclear complexes

depends on the molar stoichiometry of reactants (i.e.

on the molar ratio between metal ions and ligands)

and the pH of the water solution. Bailey et al. [8] studied

2194 P. Kopel et al. / Polyhedron 23 (2004) 2193–2202

the influence of pH and different stoichiometry on the

formation of CoII, CuII and CdII complexes in detail.

Moreover, they have found that the complexes can be

used as precursors for the preparation of transition me-

tal sulfide nanomaterials. To date, X-ray crystal struc-

tures of some complexes involving trithiocyanurateanions have been determined, e.g. [{Os3H(CO)10}3(ttc)]

[9], [{Co(en)2}2(ttc)](ClO4)3 Æ 2H2O (en = ethylenediam-

ine) [10], [{Cu(PPh3)}6(ttc)2] (PPh3 = triphenylphos-

phine) [11], [{Au(ttc)}{Au(PPhMe2)2}]2, [(AuPPh3)3(ttc)] Æ 2DMF [12], [(AuPPh3)3(ttc)] Æ 2Et2O, [Au6(L)4(tt-

c)2] Æ C6H5NO2, (L = t-butylcyanate) [13], [(SnPh3)3(ttc)], [(SnMe3)3(ttc)] [14], Ca(ttcH2)2 Æ 11H2O, Sr(ttc-

H2)2 Æ 11H2O, Ba(ttcH2)2 Æ 4.5H2O [15], Mg(ttcH2)2 Æ6H2O, Ba(ttcH2)2 Æ 7H2O, Ba(ttcH) Æ 3H2O [16], Li(ttc-

H2) Æ 2HMPA, (HMPA = hexamethylphosphoramide)

and Li3(ttc) Æ 4THF [17,18].

Recently, we have prepared and structurally charac-

terized a series of nickel(II) complexes containing the tri-

thiocyanurate dianion and nitrogen-donor ligands [19].

It has been found that the nickel atom is both five-

and six-coordinated in these complexes and ttcH2� ismonodentately bonded only through a N atom or che-

lated via N and S atoms. All the prepared complexes

are mononuclear only. Moreover, it has been found that

ttcH2� can be also situated outside the coordination

sphere of the nickel. The latter mode is preferred in

the case when the coordination sphere of the central

atom is completely occupied by N-donor ligands such

as 1,10-phenanthroline (phen) or 2,2 0-bipyridine (bpy).The complexes of iron(II) with 2,2 0-bipyridine and

1,10-phenantholine and their derivatives are of general

interest to coordination chemists [20]. In these com-

pounds, the iron(II) ions with octahedral surroundings

can be either in a low-spin (S = 0) or in a high-spin

(S = 2) ground state. It is well known that the [Fe-

(bpy)3]2+ and [Fe(phen)3]

2+ complex cations are mostly

low-spin, but their magnetochemical behaviour also de-pends on the counter-ion used, e.g. the [Fe(bpy)3]-

(BF4)2 Æ 2H2O complex exhibits a thermally induced

low-spin to high-spin crossover [21]. The substitution

of one bpy or phen ligand by a monodentate N-donor

ligand in similar complexes can also lead to the forma-

tion of compounds where transition from a low-spin

to a high-spin state can be observed. The spin-crossover

behaviour, which can be either thermally or lightinduced, was intensively studied on the [Fe(bpy)2X2]

and [Fe(phen)2X2] complexes, where X = NCS� or

NCSe� [21].

The aim of this work was to prove the coordination

abilities of the trithiocyanurate ion to iron(II). In this

study, we used the combination of ttcH3 and N-donor

organic molecules as ligands. Here, we report X-ray

structures of two iron(II) complexes: [Fe(bpy)3](ttcH) Æ2bpy Æ 7H2O (2) and [Fe(phen)3](ttcH2)(ClO4) Æ 2CH3O-

H Æ 2H2O (6). It was also our interest to find if the

presence of the trithiocyanurate ion in the iron(II) com-

plexes can cause their spin-crossover behaviour.

2. Experimental

2.1. General procedures

The chemicals and solvents were purchased from

Aldrich co. and Lachema co. and were used as received.

The C, H, N, S analyses were carried out on an EA 1108

instrument (FISONS). IR spectra (400–4000 cm�1) were

recorded on a Nexus 670 FTIR spectrometer (Ther-

moNicolet) using KBr pellets. The diffuse-reflectancespectra (11000–35000 cm�1) were obtained on a Specord

M40 (Carl Zeiss, Jena) using the nujol technique. The

transmission Mossbauer spectra were recorded using a

Mossbauer spectrometer in constant acceleration mode

with a 57Co(Rh) source. A cryostat with closed He-cycle

(Janis Research Company, USA) was used as the basis

of a refrigerating system that allowed measurements in

the 15–300 K temperature range. Isomer shift parame-ters are related to metallic iron (with a calibration tem-

perature of 300 K).

2.2. Preparation of the complexes 1–6

2.2.1. Preparation of [Fe(bpy)2(ttcH)] Æ 2H2O (1)2,2 0-Bipyridine (bpy) (320 mg, 2 mmol) in 15 ml of

EtOH was added to an aqueous solution (10 ml) of(NH4)2Fe(SO4)2 Æ 6H2O (390 mg, 1 mmol). The mixture

was stirred at room temperature for 3 h. The white so-

lid that formed was filtered off. Consecutively, a solu-

tion of ttcNa3 Æ 9H2O (400 mg, 1 mmol) in water

(5 ml) was added dropwise to the red filtrate. Then,

the mixture was stirred for 2 h, and a red microcrystal-

line product was separated by filtration, washed with

EtOH and dried under an infra lamp at 40 �C. Yield:498 mg, 86%. Anal. Calc.: C, 47.7; H, 3.7; N, 16.9; S,

16.6. Found: C, 47.6; H, 3.5; N, 16.6; S, 17.0%. IR

(cm�1): 401w, 423m, 456m, 488w, 616w, 658w, 720w,

734m, 772s, 874m, 966w, 1021w, 1134s, 1188w, 1227s,

1323w, 1343w, 1443s, 1468vs, 1529s, 1603m, 1632m,

1723w, 1738w, 2855w, 2925m, 3072w, 3103w, 3452vs.

UV–Vis (cm�1): 18700, 20200, 28600. Mossbauer spec-

trum (300 K): doublet with isomer shift(i.s.) = 0.29 ± 0.01 mm s�1, quadrupole splitting

(q.s.) = 0.33 ± 0.01 mm s�1, half-width of the spectral

line (C) = 0.26 ± 0.01 mm s�1 and relative spectrum

area (A) = 100%.

2.2.2. Preparation of [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O

(2)A suspension of iron(II) oxalate dihydrate (180 mg,

1 mmol) and bpy (320 mg, 2 mmol) in water (50 ml)

was stirred with heating until all the yellow iron(II) oxa-

P. Kopel et al. / Polyhedron 23 (2004) 2193–2202 2195

late salt disappeared. After cooling, an aqueous solution

(5 ml) of ttcNa3 Æ 9H2O (400 mg, 1 mmol) was added

dropwise with stirring to the reaction mixture. The mix-

ture was filtered off to remove a small amount of red

precipitate, which was discarded, and the filtrate was left

for crystallization. Dark red needle like crystals suitablefor X-ray analysis were obtained after one week. They

were filtered off, washed with a small amount of EtOH

and dried in air. Yield: 270 mg, 58%. Anal. Calc.: C,

55.9; H, 4.9; N, 16.0; S, 8.5. Found: C, 55.7; H, 4.6;

N, 16.0; S, 8.2%. IR (cm�1): 423m, 457w, 473m, 551w,

571w, 620m, 639w, 657w, 668w, 734m, 766vs, 772vs,

852s, 898w, 991w, 1020w, 1040w, 1067w, 1122m,

1187vs, 1250m, 1269w, 1314m, 1427s, 1454vs, 1559m,1581m, 1602s, 1622m, 1636m, 1698w, 2041w, 2907m,

3021w, 3048m, 3065m, 3409s. UV–Vis (cm�1): 18300,

19850, 28800. Mossbauer spectrum (300 K): dou-

blet with i.s. = 0.29 ± 0.01 mm s�1, q.s. = 0.34 ± 0.01

mm s�1, C = 0.25 ± 0.01 mm s�1, A = 100%.

2.2.3. Preparation of [Fe(terpyCl)2](ttcH2)2 Æ H2O (3)Fe(ClO4)2 Æ 6H2O (125 mg, 0.34 mmol) was dissolved

in EtOH (50 ml) and 1 ml of 0.1 M HClO4 and iron

chips were added. Then, 4 0-chloro-2,2 0:6 0,2 0-terpyridine

(terpyCl) (140 mg, 0.5 mmol), dissolved in 20 ml of

EtOH, was added to the solution with stirring at room

temperature. The color of the reaction mixture turned

to violet immediately and a violet precipitate was

formed. Consecutively, MeNO2 (10 ml) was added until

all the precipitate disappeared. After that a solution ofttcNa3 Æ 9H2O (200 mg, 0.5 mmol) in 10 ml of EtOH:wa-

ter (1:1) mixture was added. A small amount of the pre-

cipitate was removed and a dark violet crystalline

product, obtained from solution after two days, was fil-

tered off, washed with EtOH and dried in air. Yield: 82

mg, 34%. Anal. Calc.: C, 45.0; H, 2.7; N, 17.5; S, 20.0.

Found: C, 44.8; H, 2.8; N, 17.4; S, 20.2%. IR (cm�1):

420w, 458s, 483m, 541s, 567m, 619w, 652w, 670w,690w, 719s, 728m, 751s, 787s, 828m, 874vs, 965w,

1019w, 1034w, 1057w, 1132vs, 1232vs, 1283m, 1346s,

1394vs, 1424vs, 1460vs, 1529vs, 1600vs, 1631s, 1737m,

1776w, 1849w, 2015w, 2112w, 2344w, 2361m, 2849vs,

2911vs, 3063s, 3410s. UV–Vis (cm�1): 17200, 19400,

28000. Mossbauer spectrum (300 K): doublet with

i.s. = 0.20 ± 0.01 mm s�1, q.s. = 0.96 ± 0.01 mm s�1,

C = 0.28 ± 0.01 mm s�1, A = 100%.

2.2.4. Preparation of [Fe(phen)2(ttcH)] Æ 2H2O (4)The procedure similar to that used for the preparation

of 1 was applied, only 1,10-phenanthroline monohydrate

(400 mg, 2 mmol) was used instead of 2,2 0-bipyridine.

Yield: 364 mg, 58%. Anal. Calc.: C, 51.7; H, 3.4; N,

15.6; S, 15.3. Found: C, 51.6; H, 3.5; N, 15.2; S, 16.1%.

IR (cm�1): 435w, 409w, 420w, 458m, 483w, 530m, 558w,620m, 671w, 722s, 775m, 845vs, 876s, 967w, 998m,

1040w, 1057w, 1133vs, 1188s, 1233vs, 1344s, 1425vs,

1485vs, 1527vs, 1578m, 1631s, 1985w, 2059w, 2247w,

2291w, 2362w, 2922m, 3070s, 3431vs. UV–Vis (cm�1):

19100, 20400, 28800. Mossbauer spectrum (300 K): dou-

blet I with i.s. = 0.29 ± 0.01 mm s�1, q.s. = 0.24 ± 0.01

mm s�1, C = 0.28 ± 0.01 mm s�1, A = 71.1%; doublet II

with i.s. = 0.25 ± 0.01mm s�1, q.s. = 0.83 ± 0.01mm s�1,C = 0.29 ± 0.01 mm s�1, A = 28.9%.

2.2.5. Preparation of [Fe(nphen)2(ttcH)] Æ 4H2O (5)5-Nitro-1,10-phenanthroline (440 mg, 2 mmol) in

EtOH (100 ml) was added with stirring to an aqueous

solution (10 ml) of (NH4)2Fe(SO4)2 Æ 6H2O (390 mg, 1

mmol). Then, ttcNa3 Æ 9H2O (400 mg, 1 mmol) with 1

ml of 1 M HCl in water:EtOH (1:1) mixture was addeddropwise to the solution. A dark violet product, which

appeared during the addition of the solution of ttcNa3,

was filtered off, washed with EtOH and dried under an

infra lamp at 40 �C. Yield: 482 mg, 64%. Anal. Calc.:

C, 43.0; H, 3.1; N, 16.7; S, 12.8. Found: C, 43.1; H,

2.8; N, 16.2; S, 12.5%. IR (cm�1): 409w, 420w, 428w,

458m, 482w, 505w, 538w, 618m, 657w, 669w, 721s,

734m, 755w, 810m, 843m, 859m, 907w, 1002w, 1039w,1064w, 1130s, 1189m, 1232m, 1350s, 1420s, 1458vs,

1514s, 1534vs, 1579w, 1630m, 1684w, 2925w, 3090s,

3456vs. UV–Vis (cm�1): 17900, 21600, 29000. Mossba-

uer spectrum (300 K): doublet I with i.s. = 0.29

± 0.01 mm s�1, q.s. = 0.27 ± 0.01 mm s�1, C = 0.27 ±

0.01 mm s�1, A = 20.0%, doublet II with i.s. = 0.35 ±

0.01 mm s�1, q.s. = 0.64 ± 0.01 mm s�1, C = 0.29 ±

0.01 mm s�1, A = 80.0%.

2.2.6. Preparation of [Fe(phen)3](ttcH2)(ClO4) Æ2CH3OH Æ 2H2O (6)

Fe(ClO4)2 Æ 6H2O (250 mg, 0.68 mmol) was dis-

solved in 50 ml of MeOH and 1 ml of 0.1 M HClO4

and iron chips were added. A solution of 1,10-phen-

anthroline monohydrate (400 mg, 2 mmol) dissolved

in 10 ml of MeOH was added to this mixture, withstirring at room temperature. The color of the reac-

tion mixture turned into red immediately. Finally, a

solution of ttcNa3 Æ 9H2O (400 mg, 1 mmol) in water

(5 ml) was added. A red precipitate (its composition

was identical to [Fe(phen)2(ttcH)] Æ 2H2O (4), as was

proven by elemental analysis) was filtered off and

the filtrate was left to stand at room temperature

for crystallization. A small amount of red crystalswas obtained after two weeks. The crystals were char-

acterized only by a single crystal X-ray analysis. Yield:

77 mg, 12%.

2.3. X-ray crystallography

Diffraction experiments for complexes [Fe(bpy)3]-

(ttcH) Æ 2bpy Æ 7H2O (2) and [Fe(phen)3](ttcH2)-(ClO4) Æ 2CH3OH Æ 2H2O (6), were carried out on a

2196 P. Kopel et al. / Polyhedron 23 (2004) 2193–2202

four circle j-axis KUMA KM-4 diffractometer using

graphite-monochromated MoKa radiation (k =

0.71073 A) at 120(2) K. Data collections for both

complexes were performed using a CCD detector

(KUMA Diffraction, Wroclaw). KUMA KM4RED

software was used for data reduction. Both structureswere solved by direct methods [22]. All non-hydrogen

atoms of 2 and 6 were refined anisotropically by the

full-matrix least-squares procedure [SHELXLSHELXL-97] [23]

with weight: w ¼ 1=½r2ðF o2Þ þ ð0:050P Þ2 þ 10:000P �

for 2 and w ¼ 1=½r2ðF o2Þ þ ð0:075PÞ2 þ 3:000P � for 6,

where P ¼ ðF o2 þ 2ðF c

2Þ=3. The O(1), O(5) and O(7)

atoms in 2 are disordered. All H-atom positions, ex-

cept for one hydrogen atom of O(7) in 2, were locatedfrom Fourier difference maps. In 6, two methanol

molecules are disordered over two positions and their

hydrogen atoms were not found in the Fourier differ-

ence maps. All remaining hydrogen atoms were local-

ized and their parameters were refined. The largest

peak and hole on the final difference map for 2 and

6 were 0.711 [0.11 A from H(7W)] and �0.425 [0.46

A from O(7)] e A�3, and 0.550 [0.79 A from N(5)]and �0.606 [0.61 A from C(41)] e A�3, respectively.

Important crystallographic parameters are given in

Table 1.

Table 1

Data collection and refinement parameters for [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O

Complex 2

Empirical formula C43H44FeN11O5.5S3Formula weight 954.92

Temperature (K) 120(2)

Wavelength (A) 0.71073

Crystal system monoclinic

Space group C2/c

Unit cell dimensions

a (A) 28.943(2)

b (A) 13.3723(7)

c (A) 25.485(10)

a (�) –

b (�) 116.039(4)

c (�) –

Volume (A3) 8862(4)

Z 8

Density (calc.) (g/cm3) 1.431

Absorption coefficient (mm�1) 0.542

F(0 0 0) 3976

Crystal size (mm) 0.40 · 0.15 · 0.15

Index ranges �34 6 h 6 34, �8 6 k 6

Reflections collected 23516

Independent reflections 7657 [R(int) = 0.0321]

Refinement method full-matrix least-squares

Data/restraints/parameters 7657/4/744

Goodness-of fit on F2 0.943

Final R indices [I > 2r(I)] R1 = 0.0320, wR2 = 0.078

R indices (all data) R1 = 0.0406, wR2 = 0.083

Largest differential peak and hole (e A�3) 0.711 and �0.425

2.4. Computational details

The geometry optimisations and infrared frequency

calculations of differently protonated thion-forms of

the trithiocyanuric acid (ttcH3, ttcH2� and ttcH2�) were

performed employing hybrid density functional B3LYPas implemented in the Gaussian98W [24] and Spartan�02[25] programs. All calculations were performed with the

6-31 + G* basis set and the theoretical infrared frequen-

cies were not scaled.

3. Results and discussion

3.1. Infrared and electronic spectra

The experimental vibrational frequencies with their

relative intensities are given in Section 2.2. In general,

the IR spectra of the iron(II) complexes 1–5 are quite

similar. It is typical that the IR spectra of iron com-

plexes having aromatic heterocycles such as bpy or phen

as ligands contain several bands in the regions 1400–1600 and 700–900 cm�1, which are connected with the

ring modes [m(C–C) and m(C–N)] and the ring deforma-

tion vibrations, respectively [20]. For instance, the bands

(2) and [Fe(phen)3](ttcH2)(ClO4) Æ 2CH3OH Æ 2H2O (6)

Complex 6

C41H36ClCFeN9O8S3970.27

120(2)

0.71073

triclinic

P�1

10.4767(7)

12.5987(9)

17.0441(12)

97.342(6)

103.604(6)

103.041(6)

2091.0(3)

2

1.541

0.640

1000

0.70 · 0.50 · 0.30

15, �30 6 l 6 30 �12 6 h 6 12, �14 6 k 6 14, �13 6 l 6 20

11388

7076 [R(int) = 0.0318]

on F2 full-matrix least-squares on F2

7076/4/703

1.002

4 R1 = 0.0454, wR2 = 0.1230

0 R1 = 0.0509, wR2 = 0.1269

0.550 and �0.606

P. Kopel et al. / Polyhedron 23 (2004) 2193–2202 2197

observed in the IR spectrum of the free bpy ligand at

1414, 1452, 1456 and 1578 cm�1 are shifted to higher fre-

quencies upon coordination and are observed at 1427,

1454, 1559 and 1581 cm�1 in the spectrum of 2. The

peaks connected with the ring deformation of the aro-

matic N-donor heterocycles are observed in the IR spec-tra of all the complexes at ca. 620, 720, 775, 845 and 870

cm�1 [26]. The bands observed near 3060 and 3450 cm�1

can be connected with m(Car–H) and m(Nttc–H) vibra-

tions, respectively. At this point, it is necessary to men-

tion that the interpretation of IR spectra is somewhat

difficult in connection with the fact that many vibrations

can be overlapped. However, based on the DFT/6-

31 + G* calculated infrared frequencies (see Section3.4), we can conclude that the bands connected with

the m(C–N) and m(C–S) vibrations of the 2,4,6-trimerca-

pto-1,3,5-triazine ring are observed in IR spectra of the

complexes 1–5 at 1514–1559 and 1172–1227 cm�1, and

845–874 and 420–435 cm�1, respectively.

The diffuse-reflectance spectra of 1–5 are also very

similar. The bands observed in the 17200–19100 cm�1

range may be associated with d–d transitions or identi-cally, and more probably, like the bands with the max-

ima recorded in the regions of 19850–21600 and

27500–30000 cm�1, with metal-to-ligand charge transfer

(MLCT) transitions [27].

Fig. 1. Room temperature Mossbauer spectra of the complexes 1 (A)

and 2 (B). I.s. are related to metallic iron. The solid line results from

least-squares fitting of the data to the theoretical equation.

3.2. Mossbauer spectroscopy

The hyperfine parameters of the room temperature57Fe Mossbauer spectra of the iron(II) complexes 1–5

are given in Section 2. The experimental data were fitted

by a least squares procedure with Lorentzian profilesused to determine the line positions, widths and relative

spectra areas. The continuous lines represent the compu-

ter�s fitted data. Fig. 1 demonstrates the room tempera-

ture Mossbauer spectra of complexes 1 and 2. The

spectra are almost identical with a distinct doublet with

an isomer shift i.s. = 0.29 mm s�1 and quadrupole split-

ting parameter q.s. = 0.33 and 0.34 mm s�1, respectively.

The value of the isomer shift is typical for octahedralcomplexes of iron(II) in the low-spin state. For example,

the isomer shifts measured for [Fe(bpy)3]Cl2 and [Fe

(bpy)3](ClO4)2 are 0.33 and 0.30 mm s�1, respectively

[28,29]. The octahedral coordination of iron(II) in the

complex 2 was unambiguously confirmed by X-ray

analysis.

The room temperature Mossbauer spectrum of com-

plex 3 (Fig. 2) consists of a doublet with a relatively lowvalue of isomer shift (0.20 mm s�1) corresponding to

low-spin iron(II). In the structure of this complex, two

4 0-chloro-2,2 0:6 0,2 0-terpyridines are probably coordi-

nated to the central atom in a meridional fashion, as

in complex [Fe(terpy)2](ClO4)2 [30]. This type of coordi-

Fig. 2. The room temperature Mossbauer spectrum of complex 3.

Fig. 4. The Mossbauer spectrum of complex 4 measured at 25 K.

Fig. 3. The room temperature Mossbauer spectra of the complexes 4

(A) and 5 (B) with the results of their mathematical deconvolution

(curves I, II).

2198 P. Kopel et al. / Polyhedron 23 (2004) 2193–2202

nation leads to a lowering of the symmetry in the iron

environment resulting in the relatively high value of

the quadrupole splitting (0.96 mm s�1).

The room temperature Mossbauer spectra of thecomplexes 4 and 5 are composed of two doublets corre-

sponding to two non-equivalent coordination modes of

iron (see Fig. 3). In the spectrum of 4 (Fig. 3A), the dou-

blet I with relative spectrum area A = 71.1% shows

hyperfine parameters well comparable to those found

for complexes 1 and 2. Therefore, we can suggest that

this doublet also corresponds to octahedrally coordi-

nated low-spin iron(II), where iron is coordinated byfour N-atoms of two phen ligands and S and N atoms

of trithiocyanurate(2-). The doublet II (A = 28.9%) has

a significantly higher q.s. value (0.83 mm s�1) indicating

distortion from the octahedral coordination geometry.

We assume that the trithiocyanurate anion is coordi-

nated to iron(II) only via a N atom as in the case of

[Ni (taa)(ttcH)] {taa = tris-(2-aminoethyl)amine} [31]

or in [Cu(PPh3)2(ttcH2)] [32]. Two doublets in the room

temperature Mossbauer spectrum of complex 5 (Fig. 3B)

can be interpreted as well as in the former case. How-

ever, the relative spectral areas proved the higher con-

tent of iron atoms with a distorted octahedral

environment (AII = 80%) in comparison with complex

4. The higher tendency towards the distorsion of theoctahedral Fe environment in the case of complex 5

can be assigned to the effect of NO2 groups although

the influence of water of crystallization cannot be ex-

cluded. The low temperature Mossbauer spectra

(25 K) of the complexes 4 and 5 are very similar (the

spectrum of complex 4 is depicted in Fig. 4) and show

only one component with a high value of i.s. = 0.40

mm s�1 due to the temperature shift and q.s. = 0.17mm s�1. It is evident that the distortion is eliminated

by temperature lowering as can be deduced on the basis

of the absence of second doublet in the spectrum. The

subsequent heating to room temperature caused the re-

peated appearance of two doublets in the spectrum that

indicates a thermally induced reversible character of the

structural ordering.

In general, the obtained results are in good accord-ance with the literature data for iron(II) low-spin com-

plexes [21]. The found values of q.s. parameters

indicate the differences in the symmetry of central atom

environment and reflect the non-equivalent coordina-

tion modes of individual complexes.

Fig. 5. Molecular structure of [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O (2). Solvent water molecules and the hydrogen atoms of coordinated bpy ligands are

omitted for clarity.

Fig. 6. Molecular structure of [Fe(phen)3](ttcH2)(ClO4) Æ 2CH3OH Æ 2H2O (6). Molecules of solvents as well as hydrogen atoms of phen ligands are

omitted for clarity.

P. Kopel et al. / Polyhedron 23 (2004) 2193–2202 2199

3.3. X-ray structures

The molecular structures of 2 and 6 are shown in

Figs. 5 and 6. Selected bond lengths and angles for the

complexes are listed in Table 2. Both structures consist

of hexacoordinated [Fe(N–N)3]2+ cations (N–N = bpy

or phen) and uncoordinated trithiocyanurate anions.

There are also seven water molecules and two bpy (in

2) and one perchlorate anion, two water and two meth-

anol molecules (in 6) in the crystal lattices. Both iron(II)ions in 2 and 6 are coordinated in distorted octahedral

arrangements. The Fe–N bond lengths are quite compa-

rable and vary from 1.9715(17) to 1.9834(16) A (in 2)

and from 1.973(2) to 1.985(2) A (in 6). In both struc-

tures, the trithiocyanurate anions are situated outsidethe coordination sphere of the central atom. However,

the extent of deprotonation of the anion is different.

Only one hydrogen atom at the N(40) position of the tri-

azine ring was located in 2 (see Fig. 5), while two pro-

tons were found in 6 (see Fig. 6). It is evident that a

different manner of deprotonation causes the changes

in bond lengths and angles of the trithiocyanurate an-

ion. The C–S bond distances in 2 {1.7213(19),1.708(2), 1.7091(19) A} are intermediate between single

and double bonds (a typical value for the single C–S

bond length equals 1.81 A), whilst the C–S bond

Table 2

Selected bond lengths [A] and angles [�] in the vicinity of the central atom for [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O (2) and [Fe(phen)3](ttcH2)(ClO4) Æ 2-CH3OH Æ 2H2O (6)

Complex 2 Complex 6

Bond lengths

Fe(1)–N(25) 1.9715(17) Fe(1)–N(2) 1.973(2)

Fe(1)–N(1) 1.9721(16) Fe(1)–N(3) 1.974(2)

Fe(1)–N(13) 1.9741(16) Fe(1)–N(5) 1.978(2)

Fe(1)–N(24) 1.9775(17) Fe(1)–N(4) 1.979(2)

Fe(1)–N(12) 1.9816(16) Fe(1)–N(6) 1.980(2)

Fe(1)–N(36) 1.9834(16) Fe(1)–N(1) 1.985(2)

Bond angles

N(25)–Fe(1)–N(1) 91.01(7) N(2)–Fe(1)–N(3) 94.21(9)

N(25)–Fe(1)–N(13) 94.40(7) N(2)–Fe(1)–N(5) 93.63(9)

N(1)–Fe(1)–N(13) 172.46(7) N(3)–Fe(1)–N(5) 92.70(9)

N(25)–Fe(1)–N(24) 173.46(7) N(2)–Fe(1)–N(4) 174.07(9)

N(1)–Fe(1)–N(24) 93.34(7) N(3)–Fe(1)–N(4) 82.49(9)

N(13)–Fe(1)–N(24) 81.74(7) N(5)–Fe(1)–N(4) 91.45(9)

N(25)–Fe(1)–N(12) 94.15(6) N(2)–Fe(1)–N(6) 91.12(9)

N(1)–Fe(1)–N(12) 81.64(7) N(3)–Fe(1)–N(6) 173.06(8)

N(13)–Fe(1)–N(12) 92.71(7) N(5)–Fe(1)–N(6) 82.52(9)

N(24)–Fe(1)–N(12) 91.31(6) N(4)–Fe(1)–N(6) 92.57(9)

N(25)–Fe(1)–N(36) 81.41(6) N(2)–Fe(1)–N(1) 82.86(9)

N(1)–Fe(1)–N(36) 94.25(6) N(3)–Fe(1)–N(1) 93.14(9)

N(13)–Fe(1)–N(36) 91.75(6) N(5)–Fe(1)–N(1) 173.40(9)

N(24)–Fe(1)–N(36) 93.39(6) N(4)–Fe(1)–N(1) 92.37(9)

N(12)–Fe(1)–N(36) 173.93(6) N(6)–Fe(1)–N(1) 91.93(9)

2200 P. Kopel et al. / Polyhedron 23 (2004) 2193–2202

distances in 6 (1.678(3), 1.665(3), 1.682(3) A) are more

characteristic for C@S double bonds (a typical value

for the double C@S bond ranges from 1.61 to 1.68 A

[18]). The bond angles of the triazine rings lie in the

ranges of 116.15(16)�–125.80(17)� (for 2) and

115.7(2)�–123.2(3)� (for 6). The actual value of the an-

gles inside the triazine ring strongly depends on the ex-

tent of deprotonation as well as on the protonation site.

3.4. DFT calculations

The DFT/6-31 + G* optimised structures of differ-

ently protonated thion-forms of the trithiocyanuric acid

(ttcH3, ttcH2� and ttcH2�) are shown in Fig. 7. The

comparison of the calculated interatomic parameters

with the experimental data (X-ray) [33] is presented inTable 3. Overall, the calculations gave a good agreement

with the experimental data. The differences between

Fig. 7. The optimised geometries of differently protonated thion-forms

of trithiocyanuric acid.

experimental and theoretical bond lengths and angles

for ttcH3, ttcH2� and ttcH2�, expressed as an average

absolute deviation, were the following (Spartan�02/Gaussian98W): 0.012/0.011 A and 1.38�/1.38� for ttcH3,

0.014/0.013 A and 1.89�/1.73� for ttcH2�, and 0.016/

0.014 A and 1.42�/1.41� for ttcH2�, respectively. As

for theoretical infrared vibrational frequencies, we have

focused our attention on interpretation of the bandsbelonging to m(C–N),m(C–S), d(CNH) and d(CNC)

vibrations. The B3LYP calculations predicted two C–

N stretching bands at 1573.8 and 1279.4 cm�1 (for

ttcH3), 1539.3 and 1209.3 cm�1 (for ttcH2�), and

1514.5 and 1175.1 cm�1 (for ttcH2�). The experiment

is consistent in finding one strong and one medium

strong band at 1577 and 1260 cm�1, as measured for

ttcH3 using the KBr technique. On the other hand, thecalculated bands at 922.1 and 444.7 cm�1 (for ttcH3),

886.4 and 431.5 cm�1 (for ttcH2�), and 842.3 and

411.3 cm�1 (for ttcH2�) can be assigned to m(C–S).The bands observed in the IR spectrum of ttcH3 at

892 and 458 cm�1 can be connected with the same vibra-

tion. The theoretical bands at 1385.0 cm�1 (for ttcH3),

1294.0 cm�1 (for ttcH2�) and 1236.7 cm�1 (for ttcH2�)

are attributable to d(CNH), while the bands at 988.7cm�1 (for ttcH3), 975.4 cm�1 (for ttcH2

�) and 961.3

cm�1 (for ttcH2�) can be assigned to d(CNC). In conclu-

sion, we can state that although the values of calculated

infrared frequencies are non-scaled, a good agreement

between theoretical and experimental data has been

found.

Table 3

Comparison of X-ray and DFT-calculated (B3LYP/6-31 + G*) bond lengths [A] and angles [�] for differently protonated thion-forms of trithiocyanuric acid ðttcH3; ttcH2ð1�Þ and ttcHð2�ÞÞ

ttcH3a X-ray Sp02 G98W ttcH2

ð1�Þ X-rayb Sp02 G98W ttcH(2�) X-rayc Sp02 G98W

S(2)–C(2) 1.650 1.650 1.651 S(1)–C(38) 1.678(3) 1.684 1.689 S(1)–C(37) 1.7213(19) 1.728 1.727

S(4)–C(4) 1.641 1.650 1.651 S(2)–C(39) 1.665(3) 1.689 1.689 S(2)–C(39) 1.708(2) 1.736 1.730

S(6)–C(6) 1.657 1.650 1.651 S(3)–C(40) 1.682(3) 1.689 1.689 S(3)–C(41) 1.7091(19) 1.736 1.730

N(1)–C(2) 1.363 1.381 1.380 N(7)–C(38) 1.344(4) 1.360 1.360 C(37)–N(42) 1.360(3) 1.376 1.370

N(1)–C(6) 1.371 1.381 1.380 N(7)–C(39) 1.389(4) 1.414 1.410 C(37)–N(38) 1.361(3) 1.376 1.370

N(3)–C(2) 1.365 1.381 1.380 N(8)–C(40) 1.341(4) 1.341 1.340 N(38)–C(39) 1.330(2) 1.327 1.320

N(3)–C(4) 1.361 1.381 1.380 N(8)–C(39) 1.353(4) 1.341 1.340 C(39)–N(40) 1.370(2) 1.386 1.380

N(5)–C(4) 1.380 1.381 1.380 N(9)–C(38) 1.357(4) 1.360 1.360 N(40)–C(41) 1.365(3) 1.386 1.380

N(5)–C(6) 1.354 1.381 1.380 N(9)–C(40) 1.385(4) 1.414 1.410 C(41)–N(42) 1.339(2) 1.327 1.320

C(2)–N(3)–C(4) 125.5 126.79 126.81 C(38)–N(7)–C(39) 123.0(2) 125.10 124.94 C(39)–N(38)–C(37) 116.15(16) 118.39 118.24

C(4)–N(5)–C(6) 124.8 126.80 126.77 C(40)–N(8)–C(39) 120.2(3) 120.19 120.50 C(41)–N(40)–C(39) 122.63(17) 122.82 122.79

C(6)–N(1)–C(2) 124.2 126.77 126.75 C(38)–N(9)–C(40) 123.2(3) 124.93 124.86 C(41)–N(42)–C(37) 117.07(16) 118.39 118.52

N(1)–C(2)–N(3) 115.1 113.26 113.24 N(7)–C(38)–N(9) 115.7(2) 112.84 112.71 N(42)–C(37)–N(38) 125.80(17) 123.60 123.55

N(3)–C(4)–N(5) 114.2 113.19 113.19 N(8)–C(39)–N(7) 118.8(3) 118.40 118.49 N(38)–C(39)–N(40) 119.71(17) 118.40 118.69

N(5)–C(6)–N(1) 115.7 113.21 113.23 N(8)–C(40)–N(9) 118.8(3) 118.40 118.43 N(42)–C(41)–N(40) 118.57(17) 118.40 118.16

N(1)–C(2)–S(2) 122.4 123.36 123.38 N(7)–C(38)–S(1) 123.1(2) 123.56 123.69 N(42)–C(37)–S(1) 116.84(15) 118.20 118.23

N(3)–C(2)–S(2) 122.4 123.37 123.37 N(9)–C(38)–S(1) 121.3(2) 125.56 123.59 N(38)–C(37)–S(1) 117.36(14) 118.20 118.23

N(3)–C(4)–S(4) 123.2 123.41 123.39 N(8)–C(39)–S(2) 121.4(2) 125.05 124.89 N(38)–C(39)–S(2) 122.06(14) 124.82 124.62

N(5)–C(4)–S(4) 122.6 123.39 123.41 N(7)–C(39)–S(2) 119.7(2) 116.57 116.58 N(40)–C(39)–S(2) 118.22(15) 116.78 116.65

N(5)–C(6)–S(6) 122.4 123.37 123.38 N(8)–C(40)–S(3) 123.0(2) 125.05 124.99 N(42)–C(41)–S(3) 123.13(15) 124.82 124.88

N(1)–C(6)–S(6) 121.9 123.41 123.38 N(9)–C(40)–S(3) 118.2(2) 116.57 116.53 N(40)–C(41)–S(3) 118.29(14) 116.78 116.92

Sp02 = Spartan�02 (Windows Version 1.0.2); G98W = Gaussian98W (Rev. A.11).a The atoms are numbered following the nomenclature used in [33] for ttcH3 Æ THF.b X-ray data for [Fe(bpy)3](ttcH) Æ 2bpy Æ 7H2O (2).c X-ray data for [Fe(phen)3](ttcH2)(ClO4) Æ 2CH3OH Æ 2H2O (6).

P.Kopel

etal./Polyhedron23(2004)2193–2202

2201

2202 P. Kopel et al. / Polyhedron 23 (2004) 2193–2202

4. Supplementary material

Crystallographic data for the structures 2 and 6 have

been deposited with the Cambridge Crystallographic

Data Centre, CCDC nos. 197713 and 197712. The cop-

ies of this information may be obtained free of chargefrom the Director, CCDC, 12 Union Road, Cambridge,

CB2 1EZ, UK (fax: +44-1223-336033; e-mail: depos-

it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

Acknowledgement

The crystallographic part of this work was supportedby the GACR (a grant no. 203/02/0436).

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