Tuning the magnetic coupling between manganese porphyrins in the 2MnIITPP⋅L assemblies, where L is 6,13-pentacenequinone, isoviolanthrone2− and {MnII(triazole−)2Pc}2−. Key role of a linker (L) in magnetic exchange

Abstract

Coordination architectures involving high-spin S = 5/2 manganese (II) tetraphenylporphyrins (MnIITPP) and a series of π-conjugated linkers have been obtained. Different molecules (isoviolanthrone, 6,13-pentacenequinone, 1,2,4-triazole anions coordinated to manganese (II) phthalocyanine [(MnII(triazole−)2Pc)]2−) in either dianion or neutral states were used as linkers in these architectures. Complexes [cryptand(K+)]2⋅[(isoviolanthrone2−)⋅{MnIITPP}2]2−⋅5C6H4Cl2 (1) and [(6,13-pentacenequinone0)⋅{MnIITPP}2]0⋅2C6H4Cl2 (2) are formed as a result of the reaction of MnIITPP with isoviolanthrone2− or MnIIIClTPP with 6,13-pentacenequinone2−. Rather weak magnetic coupling between MnII atoms is due to their large spatial separation by diamagnetic isoviolanthrone2− or pentacenequinone0 linkers. Two MnIITPP units are bridged by a paramagnetic [(MnII(triazole−)2Pc)]2− dianion linker with low-spin S = 1/2 manganese(II) atoms within Pc in [cryptand(Na+)]2⋅[(MnII(triazole−)2Pc)⋅{MnIITPP}2]2−⋅5C6H4Cl2 (3). As a result, a triple-decker homotrimetallic [(MnII(triazole−)2Pc)⋅{MnIITPP}2]2− anionic assembly is formed with three paramagnetic nuclei having S = 1/2 and 5/2 spin states, respectively. Strong antiferromagnetic coupling between high-spin outer MnIITPP and low-spin central MnIIPc units is observed in 3 with J = - 35.2 cm−1. Such coupling induces a parallel alignment of outer S = 5/2 spins antiparallel to the central S = 1/2 spin yielding the high-spin S = 9/2 state at 2 K. X-ray crystallography, spectral, magnetic susceptibility data, and EPR are in line with these assignments.