Novel Layering of Aqua and Imidazolidinyl Phenolate Bridged Cationic [CuII2(μ-L)(μ-H2O)·H2O]2Units Over CuINCS Based One-Dimensional Anionic Parallel Chains as Diamagnetic Coordination Framework Host

Abstract

The hetero valence copper-based metal−organic framework structure {[CuII2(μ-L)(μ-H2O)·H2O][CuI(1,3-NCS)2]}n (2) was constructed from the aqua-bridged [Cu2] complex [Cu2(μ-L)(μ-H2O)]ClO4·1.5H2O (1·1.5H2O) of the N4O3 coordinating heptadentate imidazolidinyl phenolate Schiff base ligand, H3L (2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine). Thiocyanate coordination induced aqua bridge cleavage and reductive extrusion lead to the formation of Cu(NCS)2− anions as a molecular building block and generation of one-dimensional (1D) anionic chains as an extended coordination framework host in 2 and quantitatively replace all the ClO4− ions from 1·1.5H2O via anion metathesis. Once formed these chains trap the original [Cu2] cationic units in a layer. The copper atoms of 2 are in a distorted square-pyramidal environments around copper ions and are held together by phenolate, imidazolidinyl, and aqua bridges at 3.29 Å intrametallic CuII···CuII separation. Within the anionic part the presence of two “symmetric” end-to-end thiocyanate bridges with CuI−SCN and CuI−NCS distances of 2.61 Å (av.) and 1.924 Å (av.), respectively, results in a CuI···CuI separation of 5.51 Å (av.) within the linear chain. The cationic part of 2 exhibits a weak ferromagnetic exchange interaction (J/kB = +13.0(5) K or J = +9.0 cm−1 and g = 2.25(1)) between the two CuII ions (S = 1/2) and implies that the complex possesses an ST = 1 spin ground state in good agreement with the M vs H data below 8 K.