Influence of structural factors on the thermal stability of zinc^(II) and boron^(III) complexes with iodo- and bromosubstituted 2,2′-dipyrrines

Highlights: • Halogenated zinc^(II) and boron^(III) dipyrrinates are thermal stable up to 179–266 °C in argon. • Intramolecular red-ox-reactions are the main cause of the lowering of stability complexes. • Stability of complexes is increased when passing from I- to Br-substituted dipyrrinates. • The obtained results are interest in the development of laser dyes and sensors for PDT. - Abstract: The results of the analysis of thermal stability for zinc ^(II) and boron ^(III) complexes with 3,3′,5,5′-tetramethyl-4-ethyl-4′-iodo-2,2-dipyrrin [HL¹], 3,3′-diamyl-4,4′-dimethyl-5,5′-dibromo-2,2′-dipyrrin [HL²] and 3,3′,5,5′-tetramethyl-4,4′-dibromo-2,2′-dipyrrin [HL³] of the composition [Zn(L¹)₂]–[Zn(L³)₂] and [BF₂L¹]–[BF₂L³] are presented. The influence of halogenation of dipyrrin ligand is manifested in decreasing thermal stability of [Zn(L)₂] and [BF₂L] when replacing 4,4′-dibromosubstituted dipyrrin on 5,5′-dibromo- or 4-monoiodosubstituted ligand. Intramolecular red-ox-reactions with participation of halogen atoms are the main cause of thermal stability lowering of dipyrrinates [Zn(L)₂] and [BF₂L] compared with alkylsubstituted analogs. The obtained results are interesting for the development of laser dyes and sensors for PDT