Cadmium(II) complexes with monoiodo- and dibromodipyrromethenes: synthesis, molecular structure, spectral-luminescent properties, and stability in solutions

Cadmium(II) chelates with 4-iodo-, 5,5´-, and 4,4´-dibromo-2,2´-dipyrromethenes (HL1, HL2, and HL3, respectively) with the composition of [CdL2] were synthesized. The influence of structural features of their molecules and properties of the medium on the characteristics of absorption and fluorescence spectra, and also on the thermodynamic stability constants in solutions was evaluated. The results of quantum chemical calculations revealed that the additional coordination interactions between the bromine atoms at the α-positions of dipyrromethene ligands and the complexing atom are possible in the molecular structure of α,α´- dibromosubstituted dipyrromethenate [Cd(L2)2] in contrast with β-halogenated analogues [Cd(L1)2] and [Cd(L3)2].