Dihalogen-substituted [MnIII(3,5-diHal-sal2323)]BPh4 salts: so similar but so different

Abstract

Three novel tetraphenylborate salts of Mn(III) complexes with the Schiff base ligands 3,5-diHal-sal₂323 are synthesized and structurally and magnetically characterized: [Mn(3,5-Br,F-sal₂323)]BPh₄ (1), [Mn(3,5-diI-sal₂323)]BPh₄ (2) and [Mn(3,5-Cl,Br-sal₂323)]BPh₄ (3). Complex 1 exhibits gradual and incomplete spin transition with T_1/2 = 169 K between high spin (S = 2) and low spin (S = 1) states. The complex 2 shows no spin-crossover and retains the high spin (HS) ground state throughout the studied temperature range (2–300 K). Finally, complex 3 demonstrates two structural phase transitions (Cc → Pc and Pc → P1), with the latter one being related to a spin crossover from the HS : HS to the intermediate HS : LS phase at 133 K. The established magneto-structural correlations are traced in comparison with previously reported dihalogen-substituted [Mn(3,5-diHal-sal₂323)] complexes with a tetraphenylborate anion.