Self-Assembly of Cluster-Based Nanoscopic Supramolecules into One-Dimensional Coordination Polymers

Abstract EN

Octahedral metal clusters [Nb6Cl12(CN)6]4−, (Mn(Salen))+ (or (Mn(7-MeSalen))+) (Salen = N,N′-ethylene-bis-(salicylidene)iminate) and ditopic organic linkers (4,4′-bpe (trans-1, 2-bis(4-pyridyl)-ethylene) or 4,4′-dpyo (4,4′-dipyridyl N,N′-dioxide)) self-assemble to form three cluster-based 1D coordination polymers: [Mn(Salen)(MeOH)2]2{(4,4′-dpyo) [(Mn(Salen))2(Nb6Cl12(CN)6)]}·2MeOH (1), {(4,4′-bpe)[(Mn(7-MeSalen))2(Mn(7-MeSalen)(H2O))2(Nb6Cl12(CN)6)]}·1.5MeCN·8H2O (2), and [(4,4′-bpe)(Mn(Salen)(H2O))2]{(4,4′-bpe)2[(Mn(Salen)(MeOH))2(Mn(Salen))2(Nb6Cl12(CN)6)][(Mn(Salen))2(Nb6Cl12(CN)6)]}·16H2O (3).

Single crystal X-ray diffraction analyses show that the frameworks of the three coordination polymers are built of heterotrimeric and/or heteropentameric supramolecular species linked by ditopic organic ligands.

The framework of 1 consists of anionic chains built of heterotrimeric dianions [(Mn(Salen))2(Nb6Cl12(CN)6)]2− (T) linked by 4,4′-dpyo.

The chains run along two directions ([0 2 −2] and [0 3 3]) leading to the formation of channels along the crystallographic (a) direction where the cations [Mn(Salen)(S)2]+ and solvent molecules are located.

Also, 2 was reported earlier, it possesses a neutral 1D chain built of neutral heterpentameric supramolecules: [(Mn(7‐MeSalen))2(Mn(7‐MeSalen)(S))2(Nb6Cl12(CN)6)] (P) linked by 4,4′-bpe ligands.

Hydrogen bonds between non-bridging cyanide ligands and coordinated solvent molecules connect the chains into 2D hydrogen-bonded frameworks.

Finally, 3 features an anionic chain, built of alternating heterotrimers [(Mn(Salen))2(Nb6Cl12(CN)6)]2− and heteropentamers [(Mn(Salen)(S))2(Mn(Salen))2(Nb6Cl12(CN)6)] linked by the organic spacer 4,4′-bpe.

The anionic charge is compensated by the in situe-assembled [Mn(Salen)(S)(4,4′‐bpe)Mn(Salen)(S)]2+ dimers.

Magnetic measurements reveal that the Mn(III) ions are well isolated and only weak magnetic interactions are observed.

The thermal stability of the three compounds was investigated.