摘要:

The significant contemporary interest in inorganic oxides reflects their structural and compositional diversity, characteristics which endow these materials with a range of physical properties that are manifested in applications to microelectronics, catalysis, sorption, solar energy conversion and heavy construction.1,2However, despite the practical and fundamental importance of solid oxides, their designed synthesis remains a challenge. One strategy employs a solid-state supramolecular approach3which exploits building blocks that are programmed by their structures and juxtapositioning of functional groups to self-assemble into complex network or framework structures. Tetrapyridylporphyrins have been demonstrated to act as effective building blocks as a consequence of their square shape and thermal stability.4,5We have recently demonstrated that tetrapyridylporphyrin is an effective building block in the design of 3-D bimetallic oxides, incorporating molybdate clusters and chains.6As part of our continuing investigations of the influences of organic molecules on inorganic oxide substructures, we have introduced tetrapyridylporphyrin into the structurally diverse class of vanadium-organophosphonates7and report the structures of two 3-D organic/inorganic oxides, [Cu(tpypor){Cu2V2O2(O3PC6H5)4}]·2H2O (1·2H2O) and [Ni(tpypor){V4O4(O3PC6H5)4}]·2H2O (2·2H2O).Compound1·2H2O was produced as dark purple plates in 30% in the hydrothermal reaction of CuSO4·5H2O, Na3VO4, tpypor, and phenylphosphonic acid at 180 °C for 46 h. Compound2·2H2O was prepared using NiSO4as the source of the secondary metal under identical conditions. The infrared spectra of1and2exhibit characteristic tpypor bands in the 750–800 cm−1range and bands in the 900–950 cm−1region attributed toν(V = O). The electronic spectrum of1in a gel exhibits a red shift of the porphyrin Soret band (410 nm), reduced extinction coefficient compared to the native porphyrin and a broadening of the Soret half-width, indicative of electronic coupling between the porphyrins.8As shown inFig. 1a, the structure of1Syntheses.1·2H2O: A mixture of CuSO4·5H2O, (0.130 g, 0.52 mmol), Na3VO4(0.060 g, 0.32 mmol), tetrapyridylporphyrin, (0.080 g, 0.12 mmol), phenylphosphonic acid (0.450 g, 2.8 mmol), and water (10.131 g, 563 mmol) was placed in a polytetrafluoroethylene-lined Parr acid digestion bomb and heated to 180 °C for 46 h to give park purple plates of1·2H2O in 30% yield. IR (KBr pellet, cm−1): 1595(m), 1437(m), 940(vs, br), 800(s), 695(m), 532(m), 468(m).2·2H2O: A mixture of NiSO4, (0.130 g, 0.49 mmol), Na3VO4(0.065 g, 0.35 mmol), tetrapyridyl porphyrin, (0.080 g, 0.12 mmol), phenylphosphonic acid (0.450 g, 2.8 mmol), and water (10.098 g, 561 mmol) was treated as for1to provide dark purple plate-like crystals of2·2H2O in 35% yield. IR (KBr pellet, cm−1): 1607(m), 1437(m), 1344(m), 1066(vs, br), 800(m), 747(s), 717(m), 694(s), 551(m), 473(m).The magnetic data were recorded on 21.32 mg and 15.41 mg polycrystalline samples of1·2H2O and2·2H2O, respectively, in the 2–300 K temperature range, using a Quantum Design MPMS-SS SQUID spectrometer. The temperature dependent magnetic data were obtained at a magnetic field ofH= 106A m−1.Crystal data.1, C32H24N4O8P2VCu1.5,Mw800.74, monoclinicP21/c,a= 14.352(2) Å,b= 28.906(3) Å,c= 7.3225(8) Å,β= 100.289(2)°,V= 2988.9(6) Å3,Z= 4,Dcalc= 1.775 g cm−3,μ= 15.40 cm−1;R1 = 0.0539 (forI> 2σ(I)),R1 = 0.0648,wR2 = 0.1244 (for 7441 independent reflections).2, C32H24N4O9P2V2Ni0.5,Mw793.73, monoclinicP21/c,a= 14.406(1) Å,b= 29.404(2) Å,c= 7.1978(5) Å,β= 99.403(2)°,V= 3008.0(4) Å3,Z= 4,Dcalc= 1.748 g cm−3,μ= 10.96 cm−1;R1 = 0.0505 (forI> 2σ(I)),R1 = 0.0659,wR2 = 0.1352 (for 10650 independent reflections).3, C48H38Cu2N4O15P4V2,Mw1263.66, triclinicP1&cmb.macr;,a= 9.7559(9)Å,b= 13.900(1) Å,c= 19.717(2) Å, α = 101.657(2)°,β= 93.949(2)°,γ= 110.477(2)°,V= 2424.6(4) Å3,Dcalc= 1.731 g cm−3,μ= 14.47 cm−1;R1 = 0.0618 (forI> 2σ(I)),R1 = 0.0763,wR2 = 0.1958 (for 11498 independent reflections). CCDC reference numbers 243671–243673. Seehttp://www.rsc.org/suppdata/ce/b4/b414430a/for crystallographic data in CIF or other electronic format.is constructed from neutral bimetallic {CuVO(O3PC6H5)2}noxide chains linked through {Cu(tpypor)} building blocks into a 3-D framework. There are two distinct Cu(ii) sites: one resides in the porphyrin pocket and displays a square planar {CuN4} coordination geometry, while the second adopts square pyramidal {CuN2O3) geometry, with the basal plane defined by pyridyl nitrogen atoms from two tpypor units and by oxygen donors from two phosphonate ligands of the chain and with a bridging oxo-group from a vanadium site in the apical position. The bimetallic oxide chains consist of a central {VO(O3PC6H5)2}2n−nchain, decorated with square pyramidal Cu(ii) units, as shown inFig. 1b. Each V(iv) site exhibits square pyramidal geometry through coordination to oxygen donors from four phosphonate groups in the basal plane and a multiply-bonded oxo group in the apical position. Each phosphorus site shares an oxygen vertex with two vanadium centers and one copper site of the chain. The oxo-vanadium/organophosphonate substructure exhibits the {(VO)2(O3PR)2} secondary building unit (SBU),9characterized by O,O′-doubly bridging phosphonates, which is common to the V/P/O class of materials.7,10In fact, the structure of the {Cu(VO)(O3PC6H5)2}nchain of1is essentially identical to that observed for the 1-D oxide [Cu(phen)VO(O3PC6H5)] (3),11suggesting that common structural motifs oligomerize from SBU's and are incorporated into a variety of materials.(a) A polyhedral representation of the structure of [Cu(tpypor){Cu2V2O2(O3PC6H5)4}]·2H2O (1·2H2O), viewed in theab-plane. Color scheme: vanadium, orange polyhedra; copper, blue square pyramids and squares; phosphorus, yellow tetrahedron; carbon, black spheres; nitrogen, blue spheres. Clickhereto access a 3D view of Fig. 1a. (b) The {Cu(VO)(O3PC6H5)2}nchain of1, viewed in theac-plane.These speculations are reinforced by the structure of2, shown inFig. 2. The structure of2is similar to that of1but with Ni(ii) in the porphyrin cavity and {VO}2+units substituting for the Cu(ii) sites on the vanadophosphonate chain. The {VO(O3PC6H5)2}2n−nsubstructure of2is essentially identical to that of1. However, the square pyramidal {Cu(ii)N2O3} sites of1are replaced by {(VO)N2O3} distorted octahedra in2, resulting in corner-sharing {V = O⋯V = O} binuclear units with the terminal oxo-group projecting outward from the chain.A view if the structure of [Ni(tpypor){V4O4(O3PC6H5)4}]·2H2O (2·2H2O) in theab-plane. Color scheme as above with the exception that the nickel sites are portrayed as purple squares. Clickhereto access a 3D view of Fig. 2.Compound1exhibits Curie paramagnetism above 50 K, with the best fit to the Curie–Weiss law givingC= 2.28 cm3K mol−1,Θ= −14 K, andχTI= −0.0014 cm3mol−1. The effective magnetic moment at 300 K of 4.19 µBis consistent with fiveS= 1/2 ions, or three Cu(ii) and two V(iv) sites. In contrast, in the case of2, the magnetism arises solely from the V(iv) sites (S= 0 for the Ni(ii) site). This observation is consistent with the appearance of a single line in the epr spectrum of2atg= 1.96. A shown inFig. 3, the dependence of the magnetic susceptibility of2at high temperature was fit to the Curie–Weiss law withC= 1.560 cm3K mol−1,Θ= −10 K, andχTI= 0.00139 cm3mol−1with a value of 3.48 µBfor the effective magnetic moment at 300 K, corresponding to a moment of 1.74 µBper V(iv) site. The temperature variation could not be fit to the simple linear tetramer model, and the introduction of three or more exchange constants resulted in ambiguous fitting to the data, suggesting the presence of both ferromagnetic and antiferromagnetic interactions.The dependence of the magnetic susceptibilityχ(□), effective magnetic momentμeff(○) and inverse susceptibility 1/χ0(▵) of2on the temperature,T. The lines drawn through the data represent the fit to the Curie–Weiss law.The thermogravimetric profile of1·2H2O exhibits a weight loss ofca.2.0% between 110 and 140 °C, corresponding to the loss of two water molecules of crystallization (2.24%, calc.). This weight loss is followed by a plateau of stability from 140 to 395 °C whereupon there is a gradual loss of weight ofca.60%, attributed to the loss of the organic moieties (57.9%, calc.), to give an amorphous mixture. The thermodiffraction pattern for1remains essentially unchanged from room temperature toca. 390 °C, whereupon the structure collapses.While the assembly of porphyrin building blocks into extended structures has witnessed significant activity,12the structures of1and2are unique with respect to the composite architecture, as well as to the role of the vanadium oxide substructure in the structural elaboration. The persistence of the 1-D {VO(O3PR)}2n−nmotif suggests preorganization in the hydrothermal reaction domain and provides further indirect evidence for oligomerization from a secondary building unit,9in this case the tetranuclear species {(VO)2(O3PC6H5)2}. The synergistic interaction of the various structural components and the coordination preferences of the secondary metals are also revealed in the direct association of Cu(ii) with the V/P/O chain in1, while in contrast, the Ni(ii) sites of2are exclusively associated with the porphyrin core.

ISSN:1466-8033    

DOI:10.1039/b414430a

出版商:RSC    

年代:2004

数据来源: RSC