Probing the effect of substituents and solvent on [Mn(R-sal-N-1,5,8,12)]BPh₄: a systematic investigation of SCO properties

In manganese(iii) complexes with BPh4- as the counter anion, the ligand field strength and non-covalent interactions between cations and anions of the flexible Schiff-base ligands (R-sal-N-1,5,8,12)(2-) are tuned by modifying the different substituents at the 5-position or 3,5-positions on the phenyl rings of the salicylaldehyde, and the magneto-structural properties of complexes 5-I-BPh4 (1), 5-tBu-BPh4 (2), 5-OCH3-BPh4 (3), naphth-BPh4 (4) and 5-Br-3-OCH3-BPh4 (5) are investigated. Complex 1 undergoes an incomplete SCO with two different Mn(iii) sites, while complexes 2 and 3 remain in the HS state throughout the entire temperature range, suggesting the absence of magnetic state conversion. Under the effect of solvent, complex 4 shows different magnetic properties. Upon solvent loss, 4 displays a more complete SCO with a T-1/2 of 140 K. In contrast to the complexes described above, complex 5 possesses two substituents, namely 5-Br and 3-OCH3. As a result, it exhibits an abrupt SCO effect due to the significantly stronger intermolecular cooperativity.