Inorganica Chimica Acta 363 (2010) 4038–4047

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Inorganica Chimica Acta

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Syntheses, structures, and spectroscopy of mono- and polynuclear lanthanidecomplexes containing 4-acyl-pyrazolones and diphosphineoxide

Fabio Marchetti a,⇑, Claudio Pettinari a,⇑⇑, Adriano Pizzabiocca a, Andrei A. Drozdov b, Sergei I. Troyanov b,Constantine O. Zhuravlev c, Sergey N. Semenov d, Yuriy A. Belousov e, Ivan G. Timokhin a

a Dipartimento di Scienze Chimiche, Università degli Studi, via S. Agostino 1, 62032 Camerino, Italyb Moscow State University, Chemistry Department, Vorobjevy Gory, 119991 Moscow, Russiac Institute of Radioengineering and Electronics of RAS, 11 Mokhovaya Street, 103907 Moscow, Russiad Department of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerlande Moscow State University, Department of Materials Sciences , Vorobjevy Gory, 119899 Moscow, Russia

a r t i c l e i n f o

Article history:Received 12 May 2010Received in revised form 27 July 2010Accepted 3 August 2010Available online 7 August 2010

Keywords:X-ray crystal structuresLuminescenceLanthanide compoundsAcylpyrazolonesDiphosphineoxides

0020-1693/$ - see front matter � 2010 Elsevier B.V. Adoi:10.1016/j.ica.2010.08.006

⇑ Corresponding author. Tel.: +39 737 402217; fax:⇑⇑ Corresponding author. Tel.: +39 737 402217; fax

E-mail address: fabio.marchetti@unicam.it (F. Marc

a b s t r a c t

Lanthanide coordination compounds are important due to their unique luminescence and magneticproperties. Direct synthesis of oligo- and polymeric Ln complexes with a predicted structure is hampereddue to high coordination numbers and unstable coordination polyhedra. A «building blocks» strategy forthe synthesis of Ln(Q)3L polymers (Ln = Eu, Tb or Gd; HQ = 1-phenyl-3-methyl-4-RC(@O)pyrazol-5-one ingeneral, in detail HQS, R = thienyl; HQCP: R = cyclopentyl; L = bis(diphenylphosphine)methane dioxidedppMO2, bis(diphenylphosphine)ethane dioxide dppEO2, and bis(diphenylphosphine)butane dioxidedppBO2) has been used: {Ln(Q)3} mononuclear fragments have been linked by dppXO2 bridges whenX = E or B, while monomeric molecular derivatives have been isolated with dppMO2. Eighteen newcomplexes were prepared, 12 of them showing a polymeric nature and 6 being monomers. Threecompounds have been structurally characterized, further confirming the hypothesized connectivitywhere metal centers have been found to exist in LnO8 square antiprismatic environments. Luminescenceproperties have been also investigated.

� 2010 Elsevier B.V. All rights reserved.

1. Introduction

In the recent years an increasing attention has been devoted tothe design and production of coordination polymers (CPs) of lan-thanides with different networks [1–3]. Lanthanide-containingsystems often exhibit intense luminescence and are potentiallyinteresting for the design of luminescent materials and devices.Due to their high coordination number and special magnetic andfluorescence properties [4], the lanthanide ions are likely to pro-vide new CPs materials that possess specific properties and desiredfeatures, as molecular magnets [5], luminescent devices [6], cata-lysts [7], molecular sieves [8], sensors for molecular recognition[9], and ion exchange [10].

The lanthanide complexes, being predominantly ionic and pos-sessing high lability in solution, usually have different coordinationenvironment on the metal ion. Even by using a unique kind ofligand, compounds with different coordination numbers can beeasily prepared. However, it prevents the formation of the regular

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+39 737 637345.: +39 737 637345.hetti).

polymeric structure. One way to avoid this problem is to employstructurally rigid secondary building blocks (SBUs) with predeter-mined geometries and coordination abilities towards linkinggroups.

Among our research on lanthanide chemistry with the family of4-acylpyrazol-5-ones [11] we have found an interesting tetraden-tate ligand H2Q2Q, with two 4-acylpyrazole-5-one moieties linkedby two methylene groups (CH2CH2), that has been recently showedto form dimeric complexes with lanthanide ions, that have provento be used as suitable rigid SBUs (secondary building units) in theconstruction of regular polymeric assemblies [12]. In fact, each Lnatom in such Ln2(Q2Q)3L2 dimers is heptacoordinated by threechelating acylpyrazolonate groups and one donor atom from theadditional neutral ligand L (L is for example water or dmf or triphe-nylphosphineoxide), and the substitution of L by ditopic ligands re-tains the rigid structure of the {Ln2(Q2Q)3} fragment, which can beused as starting material for the construction of infinite helicalchains bridged, for example, by diphosphine dioxide ligands [12].Here we report the results concerning the interaction between afamily of diphosphineoxide ligands dppXO2 with a differentnumber of bridging methylene groups (dppXO2 = Ph2P(@O)-(CH2)nP(@O)Ph2 in general, in detail: dppMO2, n = 1; dppEO2,n = 2; dppBO2, n = 4) and tris-complexes of lanthanides Ln (Ln = Eu,

F. Marchetti et al. / Inorganica Chimica Acta 363 (2010) 4038–4047 4039

Tb or Gd) with bidentate 4-acylpyrazol-5-one ligands HQ(HQ = 1-phenyl-3-methyl-4-RC(@O)pyrazol-5-one in general, indetail HQS, R = thienyl; HQCP: R = cyclopentyl).

2. Experimental

2.1. Reagents and materials

The HQ proligands HQS and HQCP were previously obtained bystandard methods [11b,13]. The diphosphines (dppM, dppE anddppB) were purchased commercially from Aldrich. Ln(NO3)3�6H2O(Ln = Eu, Tb, Gd) have been prepared by dissolving Ln2O3 (Merck)in HNO3. Solvents were used as supplied or distilled using standardmethods.

2.2. Spectroscopy and other measurements

Elemental analyses (C, H, N, S) were performed in-house withFisons Instruments 1108 CHNS-O elemental analyzer. Diffusereflectance IR spectra were recorded from 4000 to 400 cm�1 usinga Perkin–Elmer system Spectrum One 100 FT-IR spectrometer. 1Hand 31P NMR spectra were recorded on a 400 Mercury Plus Varianspectrometer operating at room temperature (400 MHz for 1H and162.1 MHz for 31P). Proton chemical shifts are reported in ppm ver-sus Me4Si, while phosphorus chemical shifts are reported in ppmversus 85% H3PO4. Melting points are uncorrected and were takenon an SMP3 Stuart instrument and on a capillary apparatus. TGA-DTA spectra were obtained with a STA 6000 Simultaneous ThermalAnalyzer Perkin–Elmer by conducting the thermal studies under aninert atmosphere of dry nitrogen. Luminescence spectra of sampleswere recorded on modified LOMO DFS-12 spectrofluorimeter withdouble monochromator (12000/mm). UV–Vis absorption spectrawere recorded with CU-2000 tool.

2.3. Syntheses

2.3.1. dppMO2

A 30% solution of H2O2 (1 ml) was added to a THF solution(10 ml) of dppM (1.0 g, 2.6 mmol) with stirring and cooling. Whenthe exothermal process finished the mixture was evaporated invacuo and its volume reduced to 2 ml and cooled. A colorlesscrystalline powder formed, which was filtered and washed withether (2 � 5 ml). IR m(cm�1): 1190 (P@O), 1121, 994, 759 [14]. 31PNMR (dmso-d6, 400 MHz): d, +24.5s.

2.3.2. dppEO2

This ligand was obtained as previously described for dppMO2 li-gand. IR m(cm�1): 1175(P@O) , 1120, 945, 758 [14]. 31P NMR(dmso-d6, 400 MHz): d, +31.5s.

2.3.3. dppBO2

This ligand was obtained as described for dppMO2. IR m(cm�1):1180 (P@O), 116, 990, 843 [14]. 31P NMR (dmso-d6, 400 MHz): d,+31.0s.

2.3.4. General procedure for the synthesis of compounds 1–18Compounds 1, 4, 7, 10, 13 and 16 where synthesized accordingly

to the following procedure: 0.05 g of HQCP or HQS (0.185 and0.176 mmol respectively), equimolar amounts of KOH and dppMO2

ligand (HQ:KOH:dppMO2 = 1:1:0.33) were mixed with 10 ml ofEtOH and heated with stirring until complete dissolution ofreactants. Then a solution of Ln(NO3)3�6H2O (0.0615 mmol withHQCP and 0.0586 mmol with HQS) in 3 ml of EtOH was addedwith stirring. A precipitate slowly formed (KNO3) which wasremoved by filtration. Then, 10 ml of H2O were added and the

mixture filtered. The powder was washed with H2O, EtOH andacetone and dried over P4O10 in vacuo for 10 h at room temper-ature.

Compounds 2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17 and 18 where syn-thesized by a different procedure: 0.05 g of HQCP or HQS (0.1846and 0.1758 mmol respectively), equimolar amounts of Et3N anddppXO2 ligand (HQ:Et3N:dppXO2 = 1:1:0.33) were mixed with10 ml of EtOH and heated with stirring until complete dissolutionof reactants. Then a solution of Ln(NO3)3�6H2O (0.0615 mmol withHQCP and 0.0586 mmol with HQS) in 3 ml of EtOH was added withstirring. By cooling the reaction mixture, a white (HQCP complexes)or pale-yellow (HQS complexes) precipitate formed. It was filtered,washed with EtOH and acetone and dried over P4O10 in vacuo for10 h at room temperature.

2.3.4.1. Eu(QS)3(dppMO2)�EtOH�H2O (1). Yellow powder. Yield 87%.M.p. 159–160 �C. Anal. Calc. for C72H63EuN6O10P2S3: C, 58.42; H,4.48; N, 5.66; S, 6.48. Found C, 58.52; H, 5.54; N, 3.94; S, 6.13%.IR m(cm�1): 3059, 1607, 1591, 1579, 1480, 1438, 1366, 1185,1121, 1059, 902, 815, 779, 690. 1H NMR (dmso-d6, 400 MHz): d,0.73t, 3.64q (5H, CH3CH2OH), 2.20br (2H, H2O), 2.48s (9H, C3–CH3 of QS), 4.06br (2H, P–CH2–P of dppMO2), 5.0br, 5.30br,5.80br, 6.80m br, 7.40m br, 7.77br, 8.12br, 8.95br (44H, N1–C6H5

and thienyl of QS and P–C6H5 of dppMO2). 31P NMR (dmso-d6,400 MHz): d, +24.7s. TGA-DTA (mg% versus �C): heating from 30to 700 �C with a speed of 10 �C/min; from 80 to 110 �C loss ofone water molecule and one ethanol molecule (total weight lossfound 4.5%, Calc. 4.3%), at 310–321 �C onset of fusion (DHfusion =35.05 kJ/mol), from 330 to 700 �C progressive decomposition, witha final residue of 42 wt.%.

2.3.4.2. Eu(QS)3(dppEO2) (2). Yellow powder. Yield 84%. M.p. 330–333 �C. Anal. Calc. for C71H57EuN6O8P2S3: C, 59.54; H, 4.01; N,5.87; S, 6.71. Found C, 58.94; H, 3.96; N, 5.80; S, 6.40%. IRm(cm�1): 3061, 1592, 1578, 1480, 1438, 1369, 1225 1161, 1102,905, 815, 743, 691. 1H NMR (dmso-d6, 400 MHz): d, 2.48br (9H,C3–CH3 of QS), 3.40br (4H, P–CH2–CH2–P of dppEO2), 5.0br,5.80br, 6.80m br, 7.50br, 7.80br, 8.08br, 8.95br (44H, N1–C6H5

and thienyl of QS and P–C6H5 of dppEO2). 31P NMR (dmso-d6,400 MHz): d, +31.3s. TGA-DTA (mg% versus �C): heating from 30to 700 �C with a speed of 10 �C/min; at 332–338 �C onset of fusion(DHfusion = 49.94 kJ/mol), from 340 to 700 �C progressive decompo-sition, with a final residue of 45 wt.%.

2.3.4.3. Eu(QS)3(dppBO2) (3). Yellow powder. Yield 83%. M.p. 333–334 �C. Anal. Calc. for C73H61EuN6O8P2S3: C, 60.04; H, 4.21; N,5.75; S, 6.59. Found C, 59.64; H, 4.13; N, 5.55; S, 6.49%. IRm(cm�1): 3061, 2927, 1645, 1609, 1577, 1477, 1433, 1366, 1229,1166, 1073, 1026, 817, 784, 692. 1H NMR (dmso-d6, 400 MHz): d,2.48br (9H, C3–CH3 of QS), 2.25br (4H, P–CH2–CH2–CH2–CH2–P ofdppBO2), 3.40br (4H, P–CH2–CH2–CH2–CH2–P of dppBO2), 4.98br,5.77br, 6.75m br, 7,47br, 7.73br, 8.05br, 8.98br (44H, N1–C6H5

and thienyl of QS and P–C6H5 of dppBO2). 31P NMR (dmso-d6,400 MHz): d, +31.1s. TGA-DTA (mg% versus �C): heating from 30to 700 �C with a speed of 10 �C/min; at 333–335 �C onset of fusion(DHfusion = 53.52 kJ/mol), from 340 to 700 �C progressive decompo-sition, with a final residue of 47 wt.%.

2.3.4.4. Tb(QS)3(dppMO2)�3H2O (4). Yellow powder. Yield 78%. M.p.154–157 �C. Anal. Calc. for C69H59N6O11P2S3Tb: C, 56.56; H, 4.06;N, 5.74; S, 6.56. Found C, 56.37; H, 3.75; N, 5.55; S, 6.33%. IRm(cm�1): 3061, 1608, 1592, 1579, 1480, 1438, 1393, 1367, 1187,1122, 1059, 903, 816, 779, 690.

2.3.4.5. Tb(QS)3(dppEO2)�2H2O (5). Yellow powder. Yield 85%. M.p.300–301 �C. Anal. Calc. for C71H61N6O10P2S3Tb: C, 57.80; H, 4.17;

4040 F. Marchetti et al. / Inorganica Chimica Acta 363 (2010) 4038–4047

N, 5.70; S, 6.52. Found C, 57.28; H, 3.81; N, 5.72; S, 6.35%. IRm(cm�1): 3061, 1606, 1591, 1578, 1479, 1437, 1369, 1227, 1160,1101, 903, 816, 742, 691.

2.3.4.6. Tb(QS)3(dppBO2) (6). Yellow powder. Yield 81%. M.p. 307–308 �C. Anal. Calc. for C73H61N6O8P2S3Tb: C, 59.75; H, 4.19; N,5.73; S, 6.56. Found C, 58.91; H, 4.47; N, 5.65; S, 6.29%. IRm(cm�1): 3062, 2926, 1643, 1608, 1579, 1525, 1477, 1437, 1366,1228, 1168, 1121, 1072, 1026, 901, 817, 782, 692.

2.3.4.7. Eu(Qcp)3(dppMO2)�H2O (7). White powder. Yield 74%. M.p.151–153 �C. Anal. Calc. for C73H63EuN6O9P2: C, 63.43; H, 4.59; N,6.08. Found C, 63.44; H, 5.27; N, 6.08%. IR m(cm�1): 3058, 2951,2866, 1593, 1497, 1467, 1437, 1398, 1364, 1189, 1075, 1001,906, 819, 780, 753, 690.

2.3.4.8. Eu(Qcp)3(dppEO2)�2H2O (8). White powder. Yield 79%. M.p.253–257 �C. Anal. Calc. for C74H67EuN6O10P2: C, 62.84; H, 4.78; N,5.94. Found C, 58.69; H, 4.80; N, 5.86%. IR m(cm�1): 3059, 2957,2867, 1627, 1611, 1596, 1531, 1493, 1437, 1375, 1304, 1171,1155, 1076, 1032, 1002, 819, 743, 728, 690.

2.3.4.9. Eu(Qcp)3(dppBO2) (9). White powder. Yield 76%. M.p. 261–264 �C. Anal. Calc. for C76H67EuN6O8P2: C, 64.91; H, 4.80; N, 5.98.Found C, 64.68; H, 5.64; N, 5.95%. IR m(cm�1): 3054, 2947, 2866,1646, 1616, 1592, 1532, 1492, 1456, 1435, 1397, 1359, 1169,1074, 993, 906, 751, 737, 723, 690.

2.3.4.10. Tb(Qcp)3(dppMO2)�H2O�EtOH (10). White powder. Yield80%. M.p. 149–152 �C. Anal. Calc. for C75H69N6O10P2Tb: C, 62.76;H, 4.85; N, 5.86. Found C, 62.66; H, 5.98; N, 5.36%. IR m(cm�1):3058, 2951, 2866, 1617, 1593, 1496, 1437, 1365, 1190, 1075,1001, 820, 780, 753, 690.

2.3.4.11. Tb(Qcp)3(dppEO2) (11). White powder. Yield 78%. M.p.263–265 �C. Anal. Calc. for C74H63N6O8P2Tb: C, 64.16; H, 4.58; N,6.07. Found C, 60.51; H, 5.29; N, 6.45%. IR m(cm�1): 3059, 2957,2867, 1629, 1597, 1531, 1495, 1452, 1376, 1307, 1173, 1156,1077, 1003, 819, 743, 690, 655.

2.3.4.12. Tb(Qcp)3(dppBO2) (12). White powder. Yield 78%. M.p.266–267 �C. Anal. Calc. for C76H67N6O8P2Tb: C, 64.59; H, 4.78; N,5.95. Found C, 63.95; H, 4.74; N, 5.82%. IR m(cm�1): 3057, 1607,1594, 1580, 1475, 1365, 1341, 1229, 1164, 1059, 903, 814, 752,718, 691.

2.3.4.13. Gd(QS)3(dppMO2) (13). Yellow powder. Yield 86%. M.p.151–153 �C. Anal. Calc. for C70H55GdN6O8P2S3: C, 59.06; H, 3.89;N, 5.90; S, 6.76. Found C, 59.81; H, 4.12; N, 5.30; S 6.21%. IRm(cm�1): 3058, 2925, 1634, 1608, 1592, 1580, 1479, 1436,1341.6, 1177, 1121, 1059, 903, 815, 778, 689.

2.3.4.14. Gd(QS)3(dppEO2)�H2O (14). Yellow powder. Yield 85%. M.p.322–325 �C. Anal. Calc. for C71H59GdN6O9P2S3: C, 58.58; H, 4.09; N,5.77; S, 6.61. Found C, 58.09; H, 3.92; N, 5.78; S, 6.65%. IR m(cm�1):3060, 1606, 1590, 1578, 1478, 1437, 1367, 1226, 1163, 1121, 1058,902, 814, 729, 690.

2.3.4.15. Gd(QS)3(dppBO2) (15). Yellow powder. Yield 88%. M.p.310–313 �C. Anal. Calc. for C73H61GdN6O8P2S3: C, 59.82; H, 4.19;N, 5.73; S, 6.56. Found C, 59.81; H, 4.14; N, 5.30; S, 6.22%. IRm(cm�1): 3058, 1608, 1592, 1579, 1477, 1436, 1365, 1341, 1310,1223, 1165, 1121, 1058, 902, 815, 752, 719, 690.

2.3.4.16. Gd(Qcp)3(dppMO2)�2H2O (16). White powder. Yield 80%.M.p. 139–143 �C. Anal. Calc. for C73H65GdN6O10P2: C, 62.38; H,

4.66; N, 5.98. Found C, 62.23; H, 5.43; N, 6.21%. IR m(cm�1): 3057,2949, 2865, 1616, 1593, 1496, 1467, 1437, 1364, 1189, 1123,1075, 1000, 906, 819, 780, 752, 690, 655.

2.3.4.17. Gd(Qcp)3(dppEO2) (17). White powder. Yield 77%. M.p.250–252 �C. Anal. Calc. for C74H63GdN6O8P2: C, 64.24; H, 4.59; N,6.07. Found C, 57.82; H, 4.80; N, 5.71%. IR m(cm�1): 3061, 2963,2868, 1627, 1611, 1596, 1531, 1494, 1437, 1376, 1305, 1172,1156, 1076, 1002, 819, 743, 728, 690.

2.3.4.18. Gd(Qcp)3(dppBO2) (18). White powder. Yield 76%. M.p.310–313 �C. Anal. Calc. for C76H73GdN6O11P2: C, 62.28; H, 5.02; N,5.73. Found C, 59.16; H, 5.18; N, 5.76%. IR m(cm�1): 3056, 2949,2868, 1620, 1595, 1479, 1437, 1369, 1293, 1158, 1077, 1002,839, 757, 737, 723, 690.

2.4. X-ray crystallography

Single crystals of 1 was obtained by slow evaporation reactionmixture in sealed glass tube. X-ray suitable single crystals 3 and12 were obtained by heating and cooling reaction mixture insealed Teflon-lined stainless steel autoclave (heating up to 130 �Cfor a 6 h, cooling to room temperature for a 48 h). XRD patternfor powders were obtained with Huber camera, 2h from 3� up to80� were investigated. The crystal structures of 1, 3 and 12 weredetermined by single-crystal X-ray diffraction experiments. Thediffraction data were collected on an IPDS (Stoe) diffractometer(Mo Ka radiation, k = 0.71073 Å, graphite monochromator) at100 K. Absorption corrections were not applied. The structureswere solved by direct methods and refined by full-matrix least-squares program on F2 using SHELXL-97 software [15]. All non-hydrogen atoms were refined anisotropically. The hydrogen atomsfor all structures were included in the calculated positions. Somecrystallographic data along with details of data collection andstructure refinement are summarized in Table 1.

3. Results and discussion

3.1. Syntheses of complexes

The synthesis of complexes has been performed in water–ethanol solution by the interaction between the salt of lanthanide,the proligand HQ, the base and the diphosphineoxide dppXO2.As starting material we prefer to use the nitrates (or perchlo-rates), as other salts (chlorides, sulfates) contain anions that cancompete with other ligands in substitution towards metal center.As a base we have used triethylamine that, being a nitrogen li-gand, has sufficient affinity to proton but low to lanthanide (Chart1). Compounds 1–18 readily precipitate from the solution. Theyhave been obtained in high yields, and have shown to be stableon air. In some cases analytical and spectral data have shownsome compounds to contain water and ethanol, which are in-volved in extended intra- or intermolecular H-bonding network(see below in the crystal structure description). While derivatives1, 4, 7, 10, 13 and 16, that contain dppMO2, are enough soluble inalcohols, acetone, dmso, dmf and chlorinate solvents, apart dmfand dmso, all the others are poorly soluble in all common sol-vents, in accordance with a polymeric structure. Further supportto this hypothesis comes from the strong difference betweenthe melting point of the latter compounds, being in the range250–330 �C, and those of 1, 4, 7, 10, 13 and 16, always lower that160 �C, due to their molecular nature. The IR spectra of thecomplexes show the C@O, C@N and C@C stretching bands(1610–1520 cm-1) of coordinated acylpyrazolonate ligand in itsdeprotonated form and the m(P@O) band of coordinated

Table 1Crystal data and refinement details for derivatives 1, 3 and 12.

1 3 12

Empirical formula C72H63EuN6O10P2S3 C73H61EuN6O8P2S3 C76H70N6O8P2TbFormula weight (g mol�1) 1482.36 1460.36 1416.24T (K) 100(2) 100(2) 100(2)Wavelength (Å) 0.71073 0.71073 0.71073Crystal system, space group monoclinic, P21/c monoclinic, C2/c monoclinic, C2/ca (Å) 14.395(2) 23.398(3) 24.703(2)b (Å) 24.452(4) 14.275(1) 15.233(1)c (Å) 18.952(3) 20.184(2) 17.493(1)a (�) 90 90 90b (�) 98.71(1) 96.10(1) 93.034(8)c (�) 90 90 90Volume (Å3) 6594(2) 6703(1) 6573.4(8)Z; Dcalc (Mg m�3) 4; 1.493 4; 1.447 4; 1.431Absorption coefficient (mm�1) 1.160 1.138 1.188Crystal size (mm3) 0.3 � 0.2 � 0.1 0.2 � 0.2 � 0.1 0.2 � 0.2 � 0.1h maximum (�) 25 24 26Reflections total (Rint) 61 894 (0.1688) 9124 (0.1535) 24 460 (0.2306)Reflections/parms in refinement 15 663/935 5591/498 7816/502Absorption correction none none noneR1 [I > 2r(I)]/ wR2 (all data) 0.0805/0.2001 0.0533/0.1274 0.0929/0.1604

The unweighted R-factor is R1 =P

(Fo � Fc)/P

Fo; I > 2r(I) and the weighted R-factor is wR2 = {P

w(Fo2 � Fc2)2/P

w(Fo2)2}1/2.

NN

Ph

OH

O

RMe

+ Ln(NO3)3.6H2O+ 3 KOH+ dppMO2

3

EtOH

N NPh

O

OR

Me

NNPh

O

OR

MeLn

NN

OO

R

Me

O O

P P

PhPh Ph

Ph

+ Ln(NO3)3.6H2O+ 3 NEt3+ dppXO2

EtOH

N NPh

O

OR

Me

NNPh

OO R

Me

Ln

NN

OO

R

Me

OP

PhPh

O P PhPh

(CH2)n

(CH2)n

OPPhPh

OP

PhPh

Ln

Ln

O

O

O O

OO

O

OO

O

O

O

O

O

2, Ln = Eu, Q = QS, X = E, n = 23, Ln = Eu, Q = QS, X = B, n = 45.2H2O, Ln = Tb, Q = QS, X = E, n = 26, Ln = Tb, Q = QS, X = B, n = 48.2H2O, Ln = Eu, Q = QCP, X = E, n = 29, Ln = Eu, Q = QCP, X = B, n = 411, Ln = Tb, Q = QCP, X = E, n = 212, Ln = Tb, Q = QCP, X = B, n = 414.H2O, Ln = Gd, Q = QS, X = E, n = 215, Ln = Gd, Q = QS, X = B, n = 417, Ln = Gd, Q = QCP, X = E, n = 218.3H2O, Ln = Gd, Q = QCP, X = B, n = 4

1.EtOH.H2O, Ln = Eu, Q = QS4.3H2O, Ln = Tb, Q = QS7, Ln = Eu, Q = QCP10.H2O, Ln = Tb, Q = QCP13, Ln = Gd, Q = QS16.2H2O, Ln = Gd, Q = QCP

R = thienyl, HQ = HQSR = cyclopentyl, HQ = HQCP

Chart 1.

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diphosphineoxide at ca 1180–1150 cm�1 [16]. Slight negativeshifts of the m(P@O) in the spectra of complexes with respect tothe free ligands have been generally observed, in accordance withthe coordination of the phosphoryl oxygen atom to the metal.Other broad absorptions between 3000 and 3500 cm�1 have beenfound in the IR spectra of hydrate-solvate compounds, due toO–H of water and/or ethanol involved in H-bonding. Thermal

studies have been carried out on selected derivatives 1–3 andshowed them to be stable up to 330–340 �C, then they progres-sively decompose. NMR studies carried out on Eu compounds1–3 show evidence of decomposition in dmso-d6 solution, thediphosphineoxide ligands being completely replaced by dmsomolecules, as confirmed by 31P NMR spectra showing resonancesdue to the free diphosphineoxides [16].

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3.2. Crystal structure description

Ln–O distances in the three structures here described are pre-sented in Table 2. Compound Eu(QS)3(dppMO2)�H2O�EtOH (1), crys-tallizes in monoclinic system, space group P21/c with one formulain asymmetric unit. Eu atoms are coordinated by oxygen atoms ofdeprotonated QS and dppMO2 ligands. Each Eu atom has CN = 8,Eu–O distances ranging from 2.33(1) to 2.49(1) Å, average value2.400 Å. A square antiprismatic environment of Eu atoms isreached by coordination of two oxygen atoms from dppMO2 mol-ecule and of six oxygens from three acylpyrazolonate ligands(Fig. 1). The dppMO2 ligand plays a chelating role, due its abilityto form six-membered chelating rings.

The structure of 1 consists of infinite chains connected byhydrogen bonds. Atoms S(2) of thienyl group and oxygens O(1)of QS and O(3) of dppMO2 molecules are linked by intermolecularH-bonding to EtOH molecule with distances O(12)–S(2) 3.053 Å,O(12)–O(1) 3.009 Å, and O(12)–O(3) 2.928 Å respectively. Betweenthe H2O molecule and nitrogen atoms N(3) and N(5) of the QS

ligands the intermolecular H bond is realized, distances beingO(12)–N(4) 2.913 Å and O(12)–N(8) 2.945 Å. The P@O bonds in 1

Table 2Selected bond lengths (Å) for derivatives 1, 3 and 12.

1 (Ln = Eu) 3 (Ln = Eu) 12 (Ln = Tb)

Ln–O1 2.403(4) 2.326(6) 2.325(5)Ln–O2 2.379(5) 2.419(8) 2.370(6)Ln–O3 2.465(5) 2.319(7) 2.388(5)Ln–O4 2.338(4) 2.41(2) 2.24(1)Ln–O5 2.49(1)a 2.43(2) 2.50(1)Ln–O6 2.33(1)b

Ln–O9 2.400(4)Ln–O10 2.394(4)Ln� � �Ln 10.131(1) 10.3993(7)

a An average value for Eu–O5 and Eu–O7 bonds is presented due to liganddisorder.

b An average value for Eu–O6 and Eu–O8 bonds is presented due to liganddisorder.

Fig. 1. ORTEP-like plot of 1 with 30% probability level. All hydrogen atoms andsolvent molecules are omitted for clarity. Only one position of the disorderedgroups is shown.

are 1.499 and 1.500 Å. This fact explains the shift of m(P@O) bandin IR spectra for this bond: 1190 and 1185 cm�1 for the free ligandand for 1 respectively.

Compounds {Tb(QCP)3(dppBO2)}1 (12) and {Eu(QS)3(dppBO2)}1(3) are coordination polymers with a chain structure crystallizingin C2/c space group. In 12 only one crystallographically indepen-dent type of Tb atom is present, with mononuclear units {Tb(QCP)3}being placed in a one elemental cell. Each Tb atom has CN = 8, thecoordination polyhedron being square antiprism (Fig. 2). Only fiveindependent types of oxygen atoms are present in the structure(O1–O5), and distorted squares O1–O3–O5–O20 and O2–O4–O10–O30 are the bases of the antiprism (Fig. 2). The Tb–O distances in12 are in the range 2.24(1)–2.50(1) Å, with an average value of2.365 Å. The distance for Tb–O1 (dppBO2) bond is 2.324 Å. Thechain is formed by linking {Tb(QCP)3} units by j2-briging moleculesof dppBO2 (Fig. 3). One QCP ligand is disordered between two sym-metrical positions. Benzene rings of this QCP ligand and the dppBO2

molecule are linked by weak p-staking interactions, the distancebetween C(12) atom of Q ligand and C(6) atom of dppBO2 beingabout 3.222 Å. The distance for P@O bonds changes from 1.481 Åin the free ligand to 1.492 Å in compound 12. The values ofm(P@O) bands are 1179 cm�1 in the IR of the free ligand and1172 cm�1 in the IR of 12.

In the structure of {Eu(QS)3(dppBO2)}1 (3), that is similar to thatpreviously described, the mononuclear fragments {Eu(QS)3} arelinked by dppBO2 bridges (Fig. 4). All Eu atoms are crystallographyindependent with a coordination polyhedron being a square antip-rism (Fig. 5). The distances Eu–O are ranged from 2.319(7) to2.43(1) Å, with an average value of 2.381 Å. A small decrease ofthese values with respect to those in compound 1 is likely due tothe formation of the polymeric structure: chain molecules havemore freedom in organization that diminishes the role of steric fac-tor. One of the acylpyrazolonate QS ligands in 3 is disordered, as inthe previous structure. As previously observed for 12, also thestructure of 3 is stabilized by stacking interactions, distancesbetween thiophenyl group and acylpyrazolone ring of nextmolecule being about 3.44 Å. Compound {Eu(QS)3(dppEO2)}1 2also was shown to be polymeric with {Eu(Q)3} units linked bybridging dppEO2, but the bad quality of structural measurementsdidn’t allow us to present a detailed discussion.

Fig. 2. ORTEP-like plot of 12 with 30% probability level. All hydrogen atoms areomitted for clarity. Only one position of the disordered groups is shown.

Fig. 3. Fragment of polymeric chain in the structure of 12. Only ipso-carbon atoms from Ph and cyclopenthyl groups are shown and all hydrogen atoms are omitted for clarity.Only one position of the disordered groups is shown.

Fig. 4. Fragment of polymeric chain in the structure of 3. Only ipso-carbon atoms from Ph and thiophene groups are shown and all hydrogen atoms are omitted for clarity.Only one position of the disordered groups is shown.

Fig. 5. ORTEP-like plot of 3 with 30% probability level. All hydrogen atoms areomitted for clarity. Only one position of the disordered groups is shown.

F. Marchetti et al. / Inorganica Chimica Acta 363 (2010) 4038–4047 4043

All the compounds structurally characterized have shownsimilar arrangement of chains along one of the crystallographicaxes. The metal–metal distances within the chains are 10.131 Åfor 3 and 10.400 Å for 12. The space between chains (characterizedby Ln� � �Ln 13.704 Å for 3 and 14.511 Å for 12) is however notsufficient to guest molecules, except dihydrogen.

3.3. Luminescence studies

It is well known that some lanthanide compounds have greatluminescence properties due to the energy transfer from organic li-gand ‘‘antenna” to a metal center [17]. When excited by a 365 nmsource, the compounds emit red (for Eu complexes) and green (forTb complexes) light. The absence of the ligand band in the lumines-cence spectra of all terbium and europium species shows a highefficiency of energy transfer from ligand to metal. The lumines-cence spectra of Eu, Tb and Gd complexes were measured in a solidstate. Intensities of luminescence compounds 2 and 4–6 at roomtemperature were very weak, while for compounds 1 and 3 theintensities were greatly increases when the temperature islowered to 77 k. This fact may be explained by another energytransfer mechanism from ligand Q to OH and CH bonds vibrations.Terbium complexes 7–9 were good luminescent materials at roomtemperature. Photoluminescence spectra of all Eu compounds(Figs. 6 and 7) exhibit one emission maximum at �615 nm area.This peak can be assigned to a 5D0–7F2 transition, while otherpeaks can assigned to 5D0–7Fx (x = 0, 1, 3, 4) transitions. In all these

Fig. 6. Luminescence spectra of derivatives 1–3.

Fig. 7. Photoluminescence spectra of derivatives 8 and 9.

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spectra the transition 5D0–7F0 showed one maximum, while thetransition 5D0–7F1 showed 3 maximums. Consequently, only onecrystallography independent type of Eu atom is present in thestructures. Ratio of intensities of about 20 have been found

between the hypersensitive 5D0–7F2 transition and the 5D0–7F1

transition, insensitive to the metal environment.This fact, and also the spitting of all 5D0–7Fx transitions, con-

firmed that the coordination polyhedra of Eu atoms were distorted

F. Marchetti et al. / Inorganica Chimica Acta 363 (2010) 4038–4047 4045

square antiprisms. Luminescence spectra of compounds 2 and 3and also of 8 and 9 are similar, and therefore the coordination poly-hedra and type of ligand coordination are similar, too. Spectra ofcompounds 1 and 7 are remarkable different with those of 2–3and 8–9, being 1 and 7 mononuclear molecular substances, wheredppMO2 acts as chelating ligand, forming a six-membered chelatering with metal atom. On the contrary, 2, 3, 8 and 9 compoundshave polymeric structure with bridging dppXO2 ligands (dppXO2 =dppEO2 or dppBO2). Consequently, the dppXO2 ligand coordinationin 1 and 7 is different with those in 2–3 and 8 and 9, but the coor-dination polyhedra are distorted square antiprisms for all com-pounds. In the luminescence spectra of 10–12 (Fig. 8) the bands

Fig. 8. Photoluminescence spe

Fig. 9. Photoluminescence spe

for 5D4–7Fx, x = 6–3 are present, while the intensity of those forx = 0, 1, 2 is very weak. The most intensive signal in all the casesoccurs at 544–545 nm due to 5D4–7F5 transition, that is typicalfor terbium derivatives. The resolution of spectra is different, fall-ing from 12 to 11 and 10, being caused by greater disordering ofthe last two structures. A weak signal in all the spectra at618 nm is due to a small admixture of europium in all terbiumsamples (deriving from impurity in terbium oxide used as a pre-cursor of terbium salt).

Luminescence spectra of Gd complexes 13, 14 and 15 at liquidnitrogen temperature are presented in Fig. 9. Luminescence ofthese complexes is caused by ligand fluorescence. Due to weak

ctra of derivatives 10–12.

ctra of derivatives 13–15.

Fig. 10. Photoluminescence spectra of derivatives 16–18.

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intensities we were not able to exactly calculate the triplet levels ofQs ligand. From spectra of 17 and 18 (Fig. 10) the energy of tripletstate for Qcp ligand has been evaluated. Spectrum of 18 was re-measured at high quality to obtain the state of triplet level at480 nm.

4. Conclusions

With the aim to expand our previous work on the field of lan-thanide-containing coordination polymers (CPs) with luminescentactivity, we have here reported 18 new derivatives of trivalent Eu,Tb and Gd containing bidentate chelating acylpyrazolonates andbidentate diphosphine dioxide ligands. While dppMO2 is onlycapable to chelate one metal center, affording molecular mononu-clear derivatives, the longer methylene chains in dppEO2 anddppBO2 allow formation of 1D coordination polymers. However,differently to previous results concerning the use of tetradentatebis(acylpyrazolonate) to create rigid dinuclear {Ln2(Q2Q)3} SBUsin the construction of regular polymeric assemblies with diphos-phine dioxide ligands, now the suitable SBUs are the mononuclear{Ln(Q)3} fragments. Moreover, these derivatives display a weakphotoluminescence at room temperature that however in case ofsome Eu compounds it greatly increases by cooling the tempera-ture to 77 K.

Acknowledgements

This work was supported by the Italian PRIN fund n.2006038447: ‘‘Materiali Ibridi Metallo-Organici Multi-funzionalicon Leganti Poliazotati”), University of Camerino, and Valle-EsinaSpA.

Appendix A. Supplementary material

Supplementary data associated with this article can be found, inthe online version, at doi:10.1016/j.ica.2010.08.006.

CCDC 772378, 772379 and 772380 contain the supplementarycrystallographic data for 1, 3 and 12. These data can be obtained

free of charge from The Cambridge Crystallographic Data Centrevia www.ccdc.cam.ac.uk/data_request/cif.

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