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Heterometallic Coordination Polymers Assembled from Trigonal Trinuclear Fe2Ni-Pivalate Blocks and Polypyridine Spacers: Topological Diversity, Sorption, and Catalytic Properties

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posted on 01.06.2015, 00:00 by Svetlana A. Sotnik, Ruslan A. Polunin, Mikhail A. Kiskin, Alexander M. Kirillov, Victoria N. Dorofeeva, Konstantin S. Gavrilenko, Igor L. Eremenko, Vladimir M. Novotortsev, Sergey V. Kolotilov
Linkage of the trigonal complex [Fe2NiO­(Piv)6] (where Piv = pivalate) by a series of polypyridine ligands, namely, tris­(4-pyridyl)­triazine (L2), 2,6-bis­(3-pyridyl)-4-(4-pyridyl)­pyridine (L3), N-(bis-2,2-(4-pyridyloxymethyl)-3-(4-pyridyloxy)­propyl))­pyridone-4 (L4), and 4-(N,N-diethylamino)­phenyl-bis-2,6-(4-pyridyl)­pyridine (L5) resulted in the formation of novel coordination polymers [Fe2NiO­(Piv)6(L2)]n (2), [Fe2NiO­(Piv)6(L3)]n (3), [Fe2NiO­(Piv)6(L4)]n·nHPiv (4), and [{Fe2NiO­(Piv)6}4{L5}6]n·3nDEF (5, where DEF is N,N-diethylformamide), which were crystallographically characterized. The topological analysis of 3, 4, and 5 disclosed the 3,3,4,4-connected 2D (3, 4) or 3,4,4-connected 1D (5) underlying networks which, upon further simplification, gave rise to the uninodal 3-connected nets with the respective fes (3, 4) or SP 1-periodic net (4,4)­(0,2) (5) topologies, driven by the cluster [Fe2Ni­(μ3-O)­(μ-Piv)6] nodes and the polypyridine μ3-L3,4 or μ2-L5 blocks. The obtained topologies were compared with those identified in other closely related derivatives [Fe2NiO­(Piv)6(L1)]n (1) and {Fe2NiO­(Piv)6}8{L6}12 (6), where L1 and L6 are tris­(4-pyridyl)­pyridine and 4-(N,N-dimethylamino)­phenyl-bis-2,6-(4-pyridyl)­pyridine, respectively. It was shown that a key structure-driven role in defining the dimensionality and topology of the resulting coordination network is played by the type of polypyridine spacer. Compounds 2 and 3 possess a porous structure, as confirmed by the N2 and H2 sorption data at 78 K. Methanol and ethanol sorption by 2 was also studied indicating that the pores filled by these substrates did not induce any structural rearrangement of this sorbent. Additionally, porous coordination polymer 2 was also applied as a heterogeneous catalyst for the condensation of salicylaldehyde or 9-anthracenecarbaldehyde with malononitrile. The best activity of 2 was observed in the case of salicylaldehyde substrate, resulting in up to 88% conversion into 2-imino-2H-chromen-3-carbonitrile.