The effect of fluorine substituents on the crystal structure and spin crossover behavior of the cation [MnIII(3,5-diHal-sal2323)]+ complex family with BPh4 anions

Mononuclear Mn(iii) cation spin-crossover complexes with Schiff base ligands 3,5-diF-sal2323 and 3,5-Br,F-sal2323 have been synthesized: [Mn(3,5-diF-sal2323)]BPh4 (1) and two polymorphic modifications (2 and 3) of [Mn(3,5-Br,F-sal2323)]BPh4. Their crystal structure and magnetic properties have been studied. The complex [Mn(3,5-diF-sal2323)]BPh4 exhibits a gradual and complete spin conversion with T1/2 = 141 K between high spin (S = 2) and low spin (S = 1) states. Two polymorphic modifications of the complex [Mn(3,5-Br,F-sal2323)]BPh4 have fundamentally different magnetic properties: one of the modifications (monoclinic, 2) shows a gradual and complete spin transition with T1/2 = 137 K, while the other (triclinic, 3) suggests a more abrupt and not complete spin transition at 22 K which is difficult to diagnose due to the competition with the zero-field splitting effects. The magneto-structural relationships were traced in comparison with dichloro-, dibromo- and mixed Br,Cl-substituted [Mn(3,5-R,R′- sal2323)] complexes with tetraphenylborate anions.