We report the structural
and magnetic properties of two
new Mn3+complex cations in the spin crossover (SCO) [Mn(R-sal2323)]+series, in lattices with seven different
counterions in each case. We investigate the effect on the Mn3+spin state of appending electron-withdrawing and electron-donating
groups on the phenolate donors of the ligand. This was achieved by
substitution of theorthoandparapositions on the phenolate donors with nitro and methoxy substituents
in both possible geometric isomeric forms. Using this design paradigm,
the [MnL1]+(a) and [MnL2]+(b) complex cations were prepared by complexation of Mn3+to the hexadentate Schiff base ligands with 3-nitro-5-methoxy-phenolate
or 3-methoxy-5-nitro-phenolate substituents, respectively. A clear
trend emerges with adoption of the spin triplet form in complexes1a–7a,with the 3-nitro-5-methoxy-phenolate
donors, and spin triplet, spin quintet and thermal SCO in complexes1b–7bwith the 3-methoxy-5-nitro-phenolate
ligand isomer. The outcomes are discussed in terms of geometric and
steric factors in the 14 new compounds and by a wider analysis of
electronic choices of Mn3+with related ligands by comparison
of bond length and angular distortion data of previously reported
analogues in the [Mn(R-sal2323)]+family. The
structural and magnetic data published to date suggest a barrier to
switching may exist for high spin forms of Mn3+in those
complexes with the longest bond lengths and highest distortion parameters.
A barrier to switching from low spin to high spin is less clear but
may operate in the seven [Mn(3-NO2-5-OMe-sal2323)]+complexes1a–7areported here which were all low spin in the solid state at room
temperature.