Supramolecular Assembly of Organophosphonate ... - ACS Publications

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Supramolecular Assembly of Organophosphonate Diesters Using Paddle-Wheel Complexes: First Examples in Porphyrin Series Published as part of the Crystal Growth & Design virtual special issue IYCr 2014 - Celebrating the International Year of Crystallography Marina A. Uvarova,† Anna A. Sinelshchikova,‡ Margarita A. Golubnichaya,† Sergey E. Nefedov,*,† Yulia Yu. Enakieva,‡ Yulia G. Gorbunova,†,‡ Aslan Yu. Tsivadze,†,‡ Christine Stern,§ Alla Bessmertnykh-Lemeune,§ and Roger Guilard§ †

Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninsky Pr. 31, Moscow, 119991, Russia Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky Pr. 31, Moscow, 119071, Russia § Université de Bourgogne, ICMUB (UMR CNRS 6302), 9 Avenue Alain Savary, BP 47870, 21078 Dijon Cedex, France

Crystal Growth & Design 2014.14:5976-5984. Downloaded from pubs.acs.org by TULANE UNIV on 01/22/19. For personal use only.

‡

S Supporting Information *

ABSTRACT: The reactions of dicopper tetrapivalate complex Cu2(μ-OOC-t-Bu)4(NCMe)2 (1) with triphenylphosphine oxide and diethyl phosphite allow paddle-wheel (PW) copper(II) complexes with phosphorus-containing axial ligands (2, 3) to be obtained. When meso-bis(diethoxyphosphoryl)porphyrins 4M were employed in this ligand exchange reaction, a series of one-dimensional (1D) homo- and heterometallic coordination polymers 5M composed of PW subunits and organophosphonate diesters were prepared and characterized by means of single crystal Xray analysis. Planar porphyrinate 4Pd and nonplanar metalloporphyrinates 4Cu and 4Ni proved to be appropriate molecular structural blocks for assembly of coordination polymers. The structural parameters of the tetrapyrrolic macrocycles incorporated into the polymer chain are determined by the nature of the metal center of the porphyrin moiety. While the geometry of palladium(II) and nickel(II) porphyrinates 4Pd and 4Ni does not change significantly in the polymer chain, saddle-shaped Cu(II) porphyrinate 4Cu exhibits a nearly planar core configuration, being coordinated to the copper centers of PW fragments by two peripheral phosphoryl groups in the polymer chain. The geometry of the tetrapyrrolic core is a key parameter influencing the structural properties of the polymeric materials. For 5Pd and for isostructural 5Cu, all metal centers of the polymeric chain are aligned. The planar macrocycles of adjacent chains are parallel and are shifted one to another in such a way that the angle between the Pd···P and Pd···Pd directions is 40.4°, and the distance between the nearest palladium(II) atoms of neighboring chains is 11.668 Å. There is no free volume in these crystals. In the crystals of 5Ni, formed by nonplanar porphyrinates, only copper atoms of the PW pivalate moiety are located in one plane, and zigzag chains are formed so that two adjacent tetrapyrrolic macrocycles are located in alternating positions with respect to this plane, the nickel atoms being displaced from this plane by 1.548 Å. This arrangement naturally leads to the formation of regular pores. The resulting channels have an effective cross-section of about 10 × 12 Å and represent ca. 18% of the volume of the crystal. The exchange reaction between the free-base porphyrin 4H2 and an excess of copper(II) pivalate complex 1 is accompanied by the metalation of the porphyrin core affording the polymer 5Cu. Moreover, self-assembly of metalloporphyrinate 4Zn is observed under studied experimental conditions, which interferes with the formation of the target mixed coordination polymers.

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INTRODUCTION

their unique structural features and useful physicochemical properties. Indeed, two metal centers are bridged in these complexes by up to four equatorial ligands affording a rigid and

Supramolecular arrays based on dinuclear paddle-wheel (PW) complexes were pioneered by Cotton’s group in the mid-1990s and have been rapidly developed into an active area of chemical research.1,2 The interest in dimetallic PW structural motifs, especially in subunits of the [M2(μ-O2C-R)4] type, for the elaboration of metal−organic materials (MOMs) arises from © 2014 American Chemical Society

Received: August 2, 2014 Revised: October 14, 2014 Published: October 15, 2014 5976

dx.doi.org/10.1021/cg501157e | Cryst. Growth Des. 2014, 14, 5976−5984

Crystal Growth & Design

Article

Scheme 1. Studied Compoundsa

a

L = NCMe (1), OPPh3 (2), OPPh(OEt)2 (3). M = H2 (4H2 ), Cu (4Cu, 5Cu), Pd (4Pd, 5Pd), Ni (4Ni, 5Ni), Zn (4Zn).

Cu2(μ-OOC-t-Bu)4(NCMe)2 (1) containing weak donor acetonitrile ligands in the axial positions. To this end, two solvates of complex 1 were prepared and characterized by single crystal X-ray diffraction analysis. In our preliminary studies, the reactions of this complex with triphenylphosphine oxide and diethyl phenylphosphonate were also investigated with the aim to find optimal experimental conditions for the synthesis of 1D polymers bearing tetrapyrrolic macrocycles linked by PW units (Scheme 1, complexes 2 and 3).

highly symmetrical structural unit. Each metal atom defines a square-planar or pyramidal configuration with regard to four equatorially coordinated ligands. The axial site provides an additional feasible place for supramolecular assembly. Moreover, a large number of metals (i.e., V, Nb, Cr, Mo, W, Tc, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, and Cu) are potentially available to form dimetallic complexes with a wide range of organic multidentate ligands.1 Taking into account the interest in PW complexes as catalysts, strong reductants, antitumor metallopharmaceuticals, photon harvesters, charge carriers, and light emitters in photovoltaic and light emitting devices,3−5 the elaboration of functional materials based on these building blocks is promising for a wide range of applications. Different synthetic strategies have been used to elaborate coordination polymers bearing PW subunits. Cotton’s group started investigations using carefully designed precursors so that some edges of the PW unit were rendered practically unreactive by using nonlabile bridges, while the remaining coordination sites were occupied by easily exchangeable ligands such as acetonitrile or chloride ions.1 Later, it has been shown that reactions of metal salts (nitrates, halides, etc.) with corresponding organic linkers under solvothermal conditions could afford desirable polymers.6,7 However, these synthetic procedures often resulted from time-consuming trial-and-error experiments. Thus, the question of whether MOMs can be synthesized from molecular PW complexes represents an attractive and highly demanded synthetic alternative. To this end, it was shown that this strategy could be used for the elaboration of “end-to-end” coordination polymers since axial ligands in PW complexes can be exchanged more easily compared to equatorial bridging ligands. For example, the treatment of dinuclear tetracarboxylate PW complexes bearing water or THF in the axial positions with polycarboxylates or nitrogen-donor linkers was widely used for assembly of PW subunits.2 However, this way for polymer elaboration is limited by the choice of an appropriate organic linker because the dimetallic tetracarboxylate units can be easily decomposed by different proton and Lewis bases. Surprisingly, organophosphonate diesters were never studied as molecular building blocks for assembly of these coordination polymers. In this work, crystalline one-dimensional (1D) coordination polymers (5M) based on dicopper tetrapivalate complexes 1 and photoactive metal 5,15-bis(diethoxyphosphoryl)porphyrinates 4M (M = Cu, Pd, Ni) were prepared, and their structures were investigated by single crystal X-ray diffraction (Scheme 1). Rather simple self-assembling of phosphoryl substituted porphyrins explains the use of the phosphonate linker.8−12 The applied synthetic methodology is based on the ligand exchange reaction using water-free dicopper pivalate complex

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EXPERIMENTAL SECTION

General. All chemicals were of commercial quality (Aldrich, Acros) and used as received. Chloroform was dried over anhydrous CaCl2, followed by distillation over CaH2. 5,15-Bis(diethoxyphosphoryl)10,20-diphenylporphyrin and Cu(II), Pd(II), Ni(II), and Zn(II) 5,15bis(diethoxyphosphoryl)-10,20-diphenylporphyrins (4M) were synthesized according to previously published methods.11−13 All experiments were carried out under Ar. IR spectra were recorded on a Nicolet Nexus FT-IR spectrophotometer using a micro-ATR accessory (Pike). Elemental analysis data were obtained using a Fisons EA1108 CHNS elemental analyzer. X-ray Crystallography of 1, 2, 3, and 5M. Green crystals of 1· 2CHCl3 very unstable at room temperature were grown by recrystallization of 1·C6H6 from a chloroform/hexane solution (1:1). Single crystals of 2·CH2Cl2 were obtained by slow evaporation of a solution of 2 in CH2Cl2/hexane (1:1) at room temperature. Single crystals of 3 were obtained by slow evaporation of a solution of 3 in CHCl3/hexane (1:1) at room temperature. Single crystals of 5Cu· 6CHCl3 and 5Pd·6CHCl3 were obtained by recrystallization of 5Cu and 5Pd, respectively, from CHCl3/hexane (1:1). Single crystals of 5Ni·2CHCl3 were obtained by recrystallization of 5Ni from CHCl3/ CH3CN (2:1). The measurements were made on a Bruker SMART APEX II diffractometer with a CCD area detector (graphite monochromator, MoKα radiation, λ = 0.71073 Å, ω-scanning). The semiempirical method SADABS was applied for the absorption correction.14 The structure was solved by direct methods and refined by the full-matrix least-squares technique on F2 with anisotropic displacement parameters for all non-hydrogen atoms. All the hydrogen atoms in the complexes were placed geometrically and included in the structure factors calculation in the riding motion approximation. All the data reduction and further calculations were performed using the SAINT and SHELXTL-97 software.15,16 CCDC reference numbers are 1017124 (1·C6H6), 1017125 (1· CHCl3), 1017126 (2), 1017127 (3), 1017128 (5Cu), 1017130 (5Pd), 1017131 (5Ni). The data can be obtained free of charge from the Cambridge Crystallographic Data Centre at www.ccdc.cam.ac.uk/ data_request/cif. Details of the data collection and structure refinement for complexes 1·C6H6-5Ni are presented in Table S3, Supporting Information. Cu2(μ-OOC-t-Bu)4(NCMe)2 (1·C6H6). Copper acetate monohydrate (1.0 g, 0.005 mol) and pivalic acid (7.0 g, 0.069 mol) were mixed and kept at 160 °C for 2 h. The obtained green solid was washed with 5977



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Figure 1. Molecular structures of the complexes Cu2(μ-OOC-t-Bu)4(NCMe)2·C6H6 (1·C6H6) (a) and Cu2(μ-OO-t-Bu)4(NCMe)2·2CHCl3 (1· 2CHCl3) (b). Hydrogen atoms are omitted for clarity. hexane (2 × 20 mL) and dissolved in hot acetonitrile (10 mL). After addition of benzene (3 mL), the solution was kept at −4 °C for 1 day. Large crystals were separated by decantation under Ar, washed with cold benzene (1 × 10 mL) and hexane (1 × 10 mL), and dried at room temperature under Ar for 5 min. The complex was obtained as green crystals in 90% (3.1 g) yield. νmax /cm−1: 2960 m, 2271 m, 1610 vs, 1578 m, 1482 s, 1457 m, 1415 vs, 1375 s, 1361 m, 1223 s, 1032 w, 937 w, 895 m, 799 m, 789 s, 619 s. According to IR data (Figure S1, Supporting Information), the crystals decompose at room temperature in air after 5−15 min, giving copper pivalate, which explains why the characterization of this compound by elemental analysis failed. Cu2(μ-OOC-t-Bu)4(OPPh3)2 (2). Triphenylphosphine oxide (78 mg, 280 mmol) was added to a solution of 1·C6H6 (100 mg, 0.145 mmol) in chloroform (5 mL). The reaction mixture was stirred for 0.5 h at room temperature, concentrated to 10 mL, and kept at −5 °C for 1 day. Small crystals were separated by decantation under Ar, washed with hexane (1 × 10 mL), and dried at room temperature under Ar. The complex was obtained as green crystals in 63% (100 mg) yield. Calcd for Cu2C56H66O10P2: C, 61.81; H, 6.11. Found: C, 61.77; H, 6.04. νmax/cm−1: 3424 br m., 3060 m, 2956 s, 2924 m., 2868 m., 1664 w, 1616 s, 1520 w, 1480 s, 1456 m, 1436 s, 1416 s, 1376 s., 1360 m, 1312 w, 1224 s, 1180 s, 1120 s, 1096 m, 1072 w, 1028 w, 1000 w, 896 m, 788 m, 756 m, 724 w, 696 w, 668 w, 620 m, 540 s, 512 w, 444 m, 412 w. Cu2(μ−OOC-t-Bu)4[OP(OEt)2Ph]2 (3). Diethyl phenylphosphonate (60 mg, 280 mmol) was added to a solution of 1·C6H6 (97 mg, 0.140 mmol) in chloroform (5 mL). The reaction mixture was stirred for 0.5 h at room temperature, concentrated to 0.5 mL, and kept at −5 °C for 1 h. Small crystals were separated by decantation under Ar, washed with hexane (1 × 10 mL), and dried at room temperature under Ar. The complex was obtained as green crystals in a quantitative yield (137 mg). Calcd for Cu2C40H66O14P2: C, 50.05; H, 6.93. Found: C, 50.16; H, 6.81. νmax/cm−1: 2958 m, 1614 vs, 1482 s, 1442 m, 1417 vs, 1377 m, 1361 m, 1214 vs, 1163 m, 1134 s, 1053 m, 1019 vs, 963 vs, 895 m, 804 m, 788 m, 751 s, 696 s. {Cu 2 (μ-OOC-t-Bu) 4 [μ-[OP(OEt) 2 ] 2 Por(Ph) 2 Cu]} n (5Cu). Method A. Complex 1·C6H6 (40 mg, 5.8 × 10−3 mmol) was added to a solution of 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin (4H2) (5 mg, 6.3 × 10−3 mmol) in chloroform (2 mL). The solution was heated to reflux until complete dissolution of the copper complex, cooled, and kept at −5 °C for 1 day. A violet solid was separated by decantation under Ar, washed with cold acetonitrile (3 ×

10 mL), benzene (1 × 5 mL), and hexane (1 × 5 mL), and dried at room temperature under Ar. The complex was obtained as violet crystals in 76% (6.0 mg) yield. The crystals decompose at room temperature in air or under reduced pressure after 10−15 min giving 5Cu as a violet powder. Calcd for Cu3C60H74N4O14P2: C, 54.27; H, 5.62; N, 4.22. Found: C, 54.25; H, 5.70; N, 4.15. νmax/cm−1: 2960 m, 1610 s, 1482 s, 1417 s, 1377 m, 1305 w, 1228 vs, 1202 w, 1124 w, 1101 w, 1063 m, 1038 m, 1013 m, 981 vs, 884 s, 804 s, 789 s, 746 vs, 712 m, 701 m, 668 m, 619 m. Method B. Complex 1·C6H6 (21 mg, 3 × 10−3 mmol) was added to a solution of copper 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin (4Cu) (2.4 mg, 3 × 10−3 mmol) in chloroform (2 mL). The solution was heated to reflux until complete dissolution of the copper complex, cooled, and kept at room temperature for 1 day. A violet solid was separated by decantation under Ar, washed with cold acetonitrile (3 × 10 mL), benzene (1 × 5 mL), and hexane (1 × 5 mL), and dried at room temperature under Ar. The crystals decompose at room temperature in air or under reduced pressure after 10−15 min giving a powder of 5Cu. The complex was obtained as violet crystals in 83% (3.3 mg) yield. Calcd for Cu3C60H74N4O14P2: C, 54.27; H, 5.62; N, 4.22. Found: C, 54.32; H, 5.72; N, 4.20. The IR spectrum of the solid was identical to that of the powder obtained using method A. {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Pd]}n (5Pd). 5Pd was prepared from 4Pd (2.5 mg, 3 × 10−3 mmol) according to method B for 5Cu. The complex was obtained as violet-brown crystals in 87% (3.5 mg) yield. The crystals decompose at room temperature in air or under reduced pressure after 10−15 min giving 5Pd as a violet-brown powder. Calcd for PdCu2C60H74N4O14P2: C, 52.58; H, 5.44; N, 4.09. Found: C, 52.56; H, 5.40; N, 4.02. νmax/cm−1: 2962 m, 1615 vs, 1531 w, 1482 m, 1460 m, 1417 s, 1376 m, 1362 m, 1225 s, 1207 w, 1163 w, 1095 w, 1039 m, 1017 s, 980 m, 886 s, 801 m, 790 m, 750 s, 703 m, 666 m, 620 m. {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Ni]}n (5Ni). Prepared from 4Ni (2.3 mg, 3 × 10−3 mmol) according to method B for 5Cu. The complex was obtained as green-violet crystals in 93% (3.7 mg) yield. The crystals decompose at room temperature in air or under reduced pressure after 10−15 min giving 5Ni as a violet-green powder. Calcd for NiCu2C60H74N4O14P2: C, 54.47; H, 5.64; N, 4.02. Found: C, 54.44; H, 5.63; N, 4.06. νmax/cm−1: 2954 m, 1615 vs, 1539 w, 1482 m, 1456 m, 1417 s, 1376 m, 1362 m, 1226 vs, 1205 w, 1163 w, 5978



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1095 w, 1063 m, 1043 m, 1013 m, 1002 m, 980 m, 890 s, 797 s, 750 s, 733 m, 700 m, 668 m, 620 m.

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RESULTS AND DISCUSSION Reaction of copper(II) acetate hydrate and pivalic acid at 160 °C affords a green solid which gives crystalline benzene or chloroform solvates 1·C6H6 and 1·2CHCl3. Both green crystals are sensitive to air moisture and should be handled in an inert atmosphere. According to X-ray diffraction data for complex 1·C6H6 (Figures 1a, S3a), two nonbonded copper(II) atoms reside at a distance of 2.6179(4) Å and are linked by four pivalate anions (Cu−O, 1.953(2)−1.963(2) Å) as it was observed early for Cu2(μ-OOC-t-Bu)4(L)2 (L = THF, O(CH2Ph)2).17,18 Two acetonitrile molecules are differently located in axial positions (Cu−N distances of 2.197(2) and 2.222(2) Å and Cu−Cu−N angles of 155.2° and 170.5°) due to the presence of the benzene solvate molecule located quite close to one of the acetonitrile molecules. In contrast to solvate 1·C6H6, in the crystals of 1·2CHCl3, each CHCl3 solvate molecule forms a hydrogen bond (C···N 3.42 Å) with the nitrogen atom of acetonitrile coordinated to the copper center in the axial position (Cu−N, 2.206(2) Å) (Figures 1b and S3b). This geometry leads to a displacement of the nitrogen atoms from the Cu···Cu line (the angle formed by Cu−Cu and N−C lines is 151.7°) which should explain the decrease of the Cu···Cu distance to 2.5803(8) Å into the dicopper tetracarboxylate moiety (Cu−O, 1.950(2)−1.964(2) Å) (Table S1, Supporting Information). These data also indicate that the PW structural motif of complex 1 is stable in noncoordinating organic solvents, such as chloroform and benzene, as well as in acetonitrile, which are suitable solvents for performing the exchange of axial ligands. Indeed, PW copper(II) complex 1 reacts smoothly with different donor compounds under these experimental conditions. For example, the ligand exchange reaction with triphenylphosphine oxide in CHCl3 proceeds in less than 30 min at room temperature affording the green centrosymmetric complex Cu2(μ-OOC-t-Bu)4(OPPh3)2 (2) in 63% yield. According to X-ray diffraction data, the central PW Cu2(μOOC-t-Bu)4 moiety preserves its geometry, showing similar Cu−O distances of 1.958(1)−1.967(1) Å and a slightly increased distance between the metal centers (Cu···Cu 2.6053(4) Å), which may be related to the higher donor ability and steric hindrance of the axial ligands (Figures 2 and S4, Table S1). The oxygen atoms of triphenylphosphine oxide molecules are bonded to the copper atoms in the axial positions. The Cu−O (2.115(1) Å) and PO (1.488(1) Å) bond lengths and the angles formed by Cu···Cu and PO lines (155°) are similar for both copper atoms. Diethyl phenylphosphonate, a weaker donor ligand,19,20 replaces the acetonitrile molecules when reacting with 1 in CHCl3 at room temperature. Green single crystals of the Cu2(μ-OOC-t-Bu)4[OPPh(OEt)2]2 complex (3) were obtained in quantitative yield and investigated by X-ray diffraction (Figures 3 and S5). Once again, the structural parameters of the dicopper tetracarboxylate fragment are similar to those observed in PW copper(II) complexes 1 and 2. Indeed, the metal−metal distance is 2.6130(6) and 2.6177(6) Å (in the two independent molecules), and the Cu−O bond lengths range from 1.957(2) to 1.969(2) Å. Moreover, the oxygen atoms of phosphoryl groups are located in the axial positions at a distance of 2.132(2) and 2.150(2) Å from the copper atoms,

Figure 2. Molecular structure of the complex Cu2(μ-OOC-tBu)4(OPPh3)2 (2). Hydrogen atoms are omitted for clarity.

Figure 3. Molecular structure of the complex Cu2(μ-OOC-tBu)4[O=PPh(OEt)2]2 (3). Hydrogen atoms are omitted for clarity.

and the angle delimited by the Cu···Cu and OP lines are 150.9° and 151.0°. These values are similar to those observed for 2. Thus, ligand exchange reactions of dicopper(II) tetrapivalate complex 1 possessing labile axial acetonitrile ligands with phosphine oxide or diester phosphonate proceed selectively in CHCl3 at room temperature affording dicopper(II) tetrapivalate complexes bearing weak phosphoryl donors in axial positions. As expected, the reaction of complex 1 with 5,15bis(diethoxyphosphoryl)-10,20-diphenylporphyrin (4H 2 ) bearing two phosphoryl groups at the periphery of the tetrapyrrolic macrocycle under these experimental conditions leads to a 1D polymer due to the coordination of two phosphoryl groups to the copper atoms of two PW units. However, the metalation of porphyrin 4H2 by dicopper pivalate occurs spontaneously, and the reaction affords {Cu2(μ-OOC-tBu)4[μ-[OP(OEt)2]2Por(Ph)2Cu]}n (5Cu) as a solvate with six chloroform molecules (76% yield) (Figures 4 and S6). It is well-known that the reactivity of porphyrins in metalation reactions is determined by electronic and steric effects of peripheral substituents.21,22 Then in the case of compound 4H2, the two electron-withdrawing diethoxyphosphoryl sub5979



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Figure 4. Molecular structure of the complex {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Cu·6CHCl3]}n (5Cu·6CHCl3). Hydrogen atoms and chloroform molecules are omitted for clarity.

stituents (Hammett substituent constant 0.60)23 facilitate the metalation of the tetrapyrrolic macrocycle.24 Polymer 5Cu was also obtained in high yield (83%) by reacting dicopper(II) complex 1 with porphyrinate 4Cu in CHCl3 at room temperature. According to X-ray data, both phosphoryl groups of each porphyrin molecule are coordinated to the copper(II) ions of two PW units leading to a regular alternation of structural motifs in infinite zigzag chains (Figure 4). Thus, in these crystals, copper(II) atoms exist in two different environments. The metal atoms located at the center of the porphyrin cavities adopt a square-planar CuN4 coordination geometry. The metal centers incorporated in the PW fragment show a squarepyramidal CuO5 geometry, being ligated by equatorial pivalates and apical phosphoryl groups belonging to porphyrin molecules. Six CHCl3 solvent molecules are also present in the crystal, but the atoms of polymeric chains do not form any significant contacts with these species. The structural parameters of the PW moiety for 5Cu· 6CHCl3 resemble those reported above for discrete complexes 2 and 3 (Table S1). The metal−metal distance of 2.5701(6) Å is only slightly shorter than the one observed for 2 and 3. The Cu−O bond lengths (1.956(2)−1.966(2) Å) and structural parameters of the phosphoryl group are also similar to those obtained for 2 and 3 (Cu−O, 2.124(2) Å; Cu···Cu/OP angle, 147.3°) (Tables S1 and S2). The copper atom of the porphyrin moiety is located within the porphyrin plane (the deviation of the copper ion from the N4 plane is 0 Å), and the Cu−N distances are in the range of 1.998(2)−2.007(2) Å. The porphyrin macrocycle is almost planar, and the maximal displacement of the C(8) atom from the CuN4 plane is ±0.260 Å. The comparison of structural parameters of the copper(II) porphyrinate moiety involved in the 1D chain of 5Cu with those observed in discrete complex 4Cu(a)12 (Figure S7a, Supporting Information) points out the crucial influence of the coordination of peripheral phosphoryl groups to copper(II) atoms on the geometry of the tetrapyrrolic macrocycle (Table S2, Supporting Information). Indeed, in the crystal of 4Cu(a), the copper(II) ion adopts a distorted square-planar environment, being coordinated by four

nitrogen atoms of the nonplanar porphyrin macrocycle (Cu(1)−N(1)/(1A), 1.993(3) Å; Cu(1)−N(2)/(2A), 2.005(3) Å). The angle between the CuN(1)N(2) and CuN(1A)N(2A) planes is 8.2°, and the displacement of the four pyrrole nitrogen atoms from the mean porphyrin plane is within ±0.100 Å. Four pyrrole rings are considerably distorted in an alternate fashion, deviating either upward or downward with respect to the mean N4 plane. The geometry of the copper(II) porphyrinate moiety observed for 5Cu·6CHCl3 is rather similar to those reported earlier for the second polymorph 4Cu(b)12 (Figure S7b). This polymorph results from an axial coordination of the oxygen atom of a phosphoryl group from one porphyrin molecule to the copper center of another molecule (Cu···O, 2.649(3) Å) (Table S2). In this crystalline form, the porphyrin macrocycle is almost planar (the maximal deviation of the β-carbon atoms of the macrocycle is ±0.314 Å), and the copper atom has a squareplanar environment with the four nitrogen atoms of the porphyrin macrocycle (Cu(1)−N(1)/(1A), 2.015(2) Å; Cu(1)−N(2)/(2A), 2.022(1) Å). It has to be noted that the coordination to the PW dicopper moiety does not significantly change the geometry and orientation of diethoxyphosphoryl substituents. Indeed, the displacement of the phosphorus atom from the N4 plane is ±0.210 Å (±0.295 in 4Cu(a)), the P(1)−C(10) distance is 1.807(4) Å (1.806(3) Å in 4Cu(a)). The dihedral angle between the CuN4 and O(1)P(1)C(5) planes is 13.8° for the complex 5Cu·6CHCl3 as compared to 4Cu(a) (14.6°). The comparison of structural parameters for compounds 4Cu(a), 4Cu(b), and 5Cu·6CHCl3 points out the influence of the coordination of a peripheral donor group to the metal center on the configuration of the porphyrin macrocycle. This influence is well-known for metalloporphyrin self-assemblies resulting from the axial coordination of a peripheral substituent of one macrocycle to the metal center of another molecule. The change in the geometry of the macrocyclic core owing to the binding of a donor group to a metal ion located outside of the macrocycle is rather unexpected, even taking into account that the geometry of the porphyrinate in the solid state is a rather complicated interplay of many factors. These data are 5980



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Figure 5. Molecular structure of the complex {Cu2(μ−OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Pd]·6CHCl3}n (5Pd·6CHCl3). Hydrogen atoms and chloroform molecules are omitted for clarity.

Figure 6. Molecular structure of the complex {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Ni]}n·2CHCl3 (5Ni·2CHCl3). Hydrogen atoms and chloroform molecules are omitted for clarity.

remarkable example demonstrating that the geometry of the porphyrinic core can be influenced even by weak interactions of the porphyrin molecule with its closed environment. To prepare heterometallic polymers using this synthetic approach, PW dicopper complex 1 was reacted with palladium(II), nickel(II), or zinc(II) porphyrinates 4Pd, 4Ni, or 4Zn. These metalloporphyrinates differ from each other in the geometry of the macrocycle and the coordination ability of the central metal ions to bind axial ligands. While crystal structures of 4Pd and 4Ni are composed of discrete molecules in the solid state, 4Zn is a two-dimensional (2D) coordination polymer formed as a result of the axial binding of phosphoryl groups of

important for better understanding of natural processes involving porphyrins. Indeed, the influence of the nonplanar distortions of metalloporphyrins on their physicochemical properties and biological functions is well recognized and stimulate intensive studies of sterically hindered nonplanar porphyrin models.25,26 The copper porphyrinates have proved to be useful compounds for studies on the origin of nonplanar distortions in porphyrins. For example, recent works have shown that copper porphyrinates can be saddle-shaped even in the absence of sterically hindered substituents. 27−29 Configuration changes in the series of phosphoryl substituted copper porphyrinates 4Cu(a), 4Cu(b), and 5Cu·6CHCl3 is a 5981



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Figure 7. Arrangement of two adjacent polymer chains in the crystal structure of 5Ni·2CHCl3..

Figure 8. Crystal packing of 5Ni·2CHCl3.

one molecule to the metal centers of other molecules.11,13 Regarding the structural parameters of 4Pd and 4Ni, it has to be noted that the metal ions are located in a nearly perfect square-planar environment defined by the four nitrogen atoms of the porphyrin macrocycles for both complexes. However, the geometry of the porphyrin macrocycle is rather different in these compounds. A strong nonplanarity of the porphyrin core is only observed for 4Ni, in which the maximal deviations of the Cβ atoms from the N4 plane are in the range of −0.659−0.595 Å. The reaction of planar palladium porphyrinate 4Pd with PW complex 1 in chloroform affords the 1D heterometallic polymer {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2Por(Ph)2Pd]}n (5Pd) in 87% yield. This complex crystallizes with six molecules of chloroform and is isostructural to 5Cu·6CHCl3 (Figures 5 and S8−S10). The PW dicopper moiety shows an obvious geometry (Cu−O, 1.960(2)−1.971(2) Å), and two metal centers are nonbonded being at a distance of 2.5723(6) Å from each other (Table S1). Structural data for the phosphoryl groups are also similar to those observed for 2 and 3 (Cu−O, 2.125(2) Å; the angle formed by the Cu···Cu and OP lines is 147.1°). It is of interest to note that the geometry of the tetrapyrrolic macrocycle of palladium porphyrinate 4Pd does not change significantly upon coordination of phosphoryl groups to the copper centers of the PW moiety. Indeed, in the crystals of 5Pd·6CHCl3, the macrocycle is still planar (the maximal deviation of the carbon atoms from the N4 plane is ±0.175 Å and ±0.169 Å for 4Pd and 5Pd·6CHCl3, respectively) (Table S2). The Pd−N distances of 2.018(2)−2.029(2) Å resemble

those observed for 4Pd (2.019(2) Å). However, the coordination of the phosphoryl groups to the copper centers influences the structural parameters of this substituent leading to a decrease in the P−C bond length from 1.825(3) to 1.807(3) Å and a change of the CC/PO angle from 2.5° to 13.1°. Nonplanar porphyrinate 4Ni also affords crystalline 1D polymer {Cu2(μ-OOC-t-Bu)4[μ-[OP(OEt)2]2(Ph)2PorNi· 2CHCl3]}n (5Ni) in 93% yield under the same reaction conditions. The crystals of this complex contain two chloroform solvate molecules. A simplified polymeric chain of 5Ni is shown in Figures 6 and S11. According to X-ray analysis, the porphyrin macrocycle is also distorted as it was observed for complex 4Ni.13 The Ni−N bond lengths are in the range of 1.903(2)−1.926(2) Å and are close to those reported for 4Ni (1.885(6)−1.909(6) Å) (Table S2). The maximal deviation of one of the nitrogen atoms from the N4 plane is 0.019 Å (±0.020 Å for 4Ni). Deviations of the β-carbons of the porphyrin ring from the N4 plane are also similar in both complexes (−0.699 and 0.620 Å for 5Ni and −0.659 and 0.595 Å for 4Ni). In contrast to 4Ni, in the crystals of 5Ni the nickel atom is 0.045 Å out of the porphyrin ring, forming with the nitrogen atoms an NiN2/NiN2 angle of 2.7°. The orientation of the phosphoryl substituent with respect to the macrocycle is very similar in the two solids as indicated by the value of the dihedral angles between the CCC and CPO planes (10.6°, 11.1° and 10.1°, 12.9°, respectively). The structure of the PW fragment is also close to those observed for analogous complexes (Table S1). 5982



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Thus, the geometry of the tetrapyrrolic macrocycle of palladium porphyrinate 4Pd and nickel porphyrinate 4Ni does not change significantly upon coordination of phosphoryl groups to the copper centers. This leads to a significant difference in the packing of polymer chains in the crystal unit for 5Pd and 5Ni. For 5Pd, as well as for isostructural 5Cu, the planar macrocycles of adjacent chains are parallel and are shifted one to another in such a way that the angle formed by the Pd···P and Cu···Cu lines is 40.4°, and the distance between the nearest palladium(II) atoms is 11.668 Å (Figure S9, Supporting Information). There is no free volume in these crystals (Figure S10, Supporting Information). In the crystals of 5Ni, formed by nonplanar porphyrinates, typical zigzag chains are observed, and two adjacent macrocycles are located in alternating positions with respect to the Cu···Cu line (Figure 7). Nickel(II) atoms are displaced by 1.548 Å from this direction. This arrangement of porphyrinate molecules induces the presence of regular pores in the crystal. The resulting channels have an effective cross-section about 10 × 12 Å and represent ca. 18% of the volume of the crystal (Figure 8). It is worth noting that we have also studied the reaction between copper(II) pivalate 1 and zinc porphyrinate 4Zn in different solvents, such as MeOH, CHCl3, MeCN, C6H6, and MeC6H5 by varying the reagent ratio and concentration. However, heterometallic polymer 5Zn was never obtained because the self-assembly of 4Zn was observed under all studied experimental conditions leading to crystalline 2D coordination polymer.11 Thus, it seems that coordination polymer 5Zn is less stable compared to the supramolecular selfassembling architecture and cannot be prepared using the ligand exchange reaction with the PW copper(II) pivalate.

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Article

ASSOCIATED CONTENT

S Supporting Information *

The IR spectra for 1·C6H6 and 5Cu, single crystal X-ray data and structure refinement for compounds 1−5Ni, and other structural informations are available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the CNRS and RAS, the Russian Foundation for Basic Research (Grant No. 12-03-93110, 12-0331339), and the Foundation of the President of the Russian Federation (MK-4452.2012.3) and was carried out in the framework of the International Associated French−Russian Laboratory of Macrocycle Systems and Related Materials (LAMREM) of CNRS and RAS. The authors thank G. A. Kirakosyan for help in the manuscript preparation.

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DEDICATION To the memory of Dr. Oleg V. Shishkin. REFERENCES

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CONCLUSIONS

PW carboxylate complexes with labile axial ligands are convenient starting compounds to prepare coordination polymers based on phosphonate diesters. In this work, a series of 1D homo- and heterometallic coordination polymers formed by metallo(phosphoryl)porphyrinates and copper(II) pivalate were obtained using this methodology. Planar and nonplanar metalloporphyrinates can be used as molecular structural blocks for polymer preparation. However, self-assembly can be observed for some metalloporphyrinate precursors under studied experimental conditions. This process can preclude the formation of the target mixed polymer, as it was observed for 4Zn. An unusual change in the geometry of the tetrapyrrolic macrocycle induced by the coordination of peripheral phosphoryl groups to the metal center was observed for the copper porphyrinate 5Cu. These data are of main interest for biomimetic studies aimed at determining the structural mechanisms controlling various biological functions of natural porphyrins. Moreover, this methodology is also useful to prepare porous materials, as it was demonstrated using nonplanar nickel porphyrinate 4Ni. Taking into account the enormous range of metals potentially available to form dimetallic PW complexes and the wide range of organophosphonate multidentate ligands, we expect that this synthetic approach will be a simple and general way to elaborate coordination polymers by using functional organic precursors. 5983



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