Influence of structural and solvation factors on spectral properties and lipophilicity of iodo- and bromosubstituted zinc(II), cadmium(II) and boron(III) dipyrromethenates

Abstract

The paper presents a comparative analysis of the effect of structural and solvation factors on the spectral characteristics and lipophilicity of a series of iodo- and bromosubstituted zinc(II), cadmium(II), and boron(III) dipyrromethethenes. The studied chelates [ZnL2], [CdL2], and [BF2L] fluoresce in organic solvents solutions with a quantum yield from 1% to 50%, depending on their molecular structure and the solvent nature. It was noted that the high sensitivity of [ZnL2] and [CdL2] fluorescence to the presence of electron- and proton-donor solvents are due to the additional coordination of M···Solv or acid-base interactions ≥ N⋯H–Solv. It was found that [BF2L] have up to 1.5 times higher lipophilicity compared to [ZnL2] with the same functional substitution. The hydrophobicity of 4,4′-dibromosubstituted luminophores is noticeably higher than that of 5,5′-dibromosubstituted analogs. The obtained results indicate the prospects for the development of new effective fluorescent markers and sensors of medium polarity based on halogen-substituted dipyrromethenates.