Supramolecular association involving nitrile–nitrile interactions in polymeric Mn(II) coordination complexes: A combined experimental and theoretical study

Abstract

Two new Mn(II) coordination polymers viz. [Mn(p-NBz)2(4-CNpy)2]n (1) and [Mn(4-CNpy)2(H2BTC)2]n (2) [p-NBz = p-nitrobenzoate, H3BTC = 1,3,5-benzenetricarboxylic acid and 4-CNpy = 4-cyanopyridine] have been synthesized at room temperature and characterized by single crystal X-ray diffraction, FT-IR spectroscopy, electronic spectroscopy, elemental analyses and thermogravimetric analysis (TGA). The complexes are stabilized by several non-covalent interactions along with a rather uncommon nitrile(π)–nitrile(π) interactions resulting in layered structures. The supramolecular association in both the polymers results in 3D network structures involving CH⋯O interactions in the direction perpendicular to the existing layers. The anti-parallel CN⋯CN interaction observed in the polymeric chains of the complexes are studied using DFT calculations and characterized using the Bader’s theory of “atoms-in-molecules”. The interaction energy of the anti-parallel nitrile–nitrile interactions is similar to hydrogen bonds which are enhanced by the coordination of 4-CNpy to the Mn(II) metal centre.