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Heteroleptic zinc dipyrromethene complexes

“…Dipyrromethene ligands and their complexes are multifaceted chromophoric systems [25] with broad absorption profiles [22,23]. As such, absorption spectroscopy is generally cumbersome for the study of dipyrromethene complexation reactions since the spectra of reaction mixtures are complicated, and there are many overlapping signals.…”

“…As such, absorption spectroscopy is generally cumbersome for the study of dipyrromethene complexation reactions since the spectra of reaction mixtures are complicated, and there are many overlapping signals. Additionally, the absorption spectra of dipyrromethenes are highly dependant upon the pH of the solution, tentatively attributed by others to protonation-deprotonation equilibria and resultant conformational changes [25,26]. Titrations involving the addition of metal salts or complexes to dipyrromethene ligands inevitably result in such pH changes, further complicating the visible spectra.…”

“…Using a combination of spectroscopic and calorimetric methods Guseva et al have recently reported on the thermodynamics of dipyrromethene deprotonation and complexation as part of their work towards understanding the metal-template effect in the synthesis of porphyrins [25,[27][28][29]. The data that Guseva uses to calculate equilibrium constants for dipyrromethene complexation with Zn(II), Ni(II), Co(II), Cu(II) and Hg(II) is extracted from the absorption maxima attributed solely to ligand and homoleptic complexes in titrations and does not take into account any intermediates, e.g.…”

Influence of metal cation on chromophore properties of complexes of some d metals with α,α-dipyrrolylmethene

“…In this work we made a comparative analysis of the electronic absorption spectra of the free ligand, 3,3`,5,5`-tetramethyl-4,4`-dibutyl-2,2`-dipyrrolylmethene I, and its complexes with Zn 2+ (II), Hg 2+ (III), Co 2+ (IV), Ni 2+ (V), and Cu 2+ (VI) [5,6] in various organic solvents: 1-propanol, benzene, DMF, pyridine, and chloroform.…”

“…In chloroform, the shift is considerably smaller and does not exceed 20 330 nm. This fact is due to specific solvation with chloroform of the heteroatom of the pyrrolenine ring (>N...HCCl 3 ) [5], causing l I L of the free ligand I to increase relative to the other solvents. The chloroform proton acts as an auxochrome similar to metal ions in the complexes, but its polarizing effect on the chromophore is considerably weaker [9].…”