Peculiar properties of homoleptic Cu complexes with dipyrromethene derivatives

Abstract

In view of preparing Cu polynuclear complexes with dipyrromethene ligands, the mononuclear complexes [Cu(II)(dipy)2] (dipyH = 5-phenyldipyrromethene) and [Cu(II)(dpdipy)2] (dpdipyH = 1,5,9-triphenyldipyrromethene) have been prepared and characterized by X-ray crystallography, mass spectrometry and EPR spectroscopy. Their peculiar redox and spectroscopic (absorption/emission) behaviours are discussed. In contrast to Cu(II) complexes of 1,1'-bidypyrrin, the reduction electrolysis of [Cu(II)(dpdipy)2] leads to decomposition products on a time scale of a few hours. Moreover in relation to this observation, [Cu(I)(dpdipy)2](-) could not be synthesized in spite of the Cu(I) core protection by the phenyl substituents in ortho position of the nitrogen atoms. Theoretical calculations provide some explanations for this instability. Interestingly [Cu(II)(dipy)2] and [Cu(II)(dpdipy)2] display weak luminescence at room temperature, attributed to a ligand centered emission.

Metal dipyrrin complexes as potential photosensitizers for photodynamic therapy

“…The nickel and copper centers in 1 and 2 (Figure 1, Table S1) 77,92,93 and 62.9 -66.9° for Cu complexes. 77,81,92,93 Consequently, the geometry of our two new molecules seems to be typical for such metal complexes. Although Ni(II) and Cu(II) complexes favor square planar coordinations, steric repulsion between the methyl groups at the α position of the dipyrrinato ligand prevent planar structures in these complexes.…”

“…[73][74][75][76][77][78][79] Although the majority of Ni(II) and Cu(II) complexes are known to be non-luminescent, some compounds including the structurally related Cu(II)(5-phenyldipyrromethene)2 and Cu(II)(1,5,9-triphenyldipyrromethene)2 complexes were previously found to be emitting. [80][81][82] Capitalising on these studies, two new compounds (complexes 1-2) were synthesised and characterised in depth, including by single crystal X-ray diffraction. Their potential as PDT PSs is reported.…”

Molecular excitons in a copper azadipyrrin complex

“…1). The electronic absorption spectrum of Cu(L-aza) 2 has been reported previously, 12,17,24 and appears anomalous compared to other M(L-aza) 2 species, with two intense bands with nearly identical oscillator strength. Furthermore, applying exciton coupling theory using structural parameters (such as dihedral angle) to calculate energy splittings and intensities fails to account for the equal intensities observed in the Cu(L-aza) 2 spectrum.…”

Bridging-arylene effects on spectroscopic and photophysical properties of arylborane–dipyrrinato zinc(ii) complexes

“…Dipyrrinato metal complexes exhibiting the CT-type excited states are characteristic at this stage since most of the excited states of dipyrrinato metal complexes are ascribed to pp* transition in the dipyrrinato ligand. [43][44][45][46][47][48][49][50][51][52] Especially, two stereoisomers of bis(5-{4-[bis (2,4,6-trimethylphenyl)boryl]phenyl}dipyrrinato)platinum(II), PtBph, possessing the square-planar and distorted tetrahedral geometries show different absorption/emission spectra not only in the MLCT/ pp*/p(aryl)-p(B) CT band but also in the ligand-centered (LC) band. Both crystallographic data and theoretical calculations suggest that a dihedral angle between the dipyrrinate and bridging phenylene moieties in the square-planar isomer is larger than that in the distorted tetrahedral one.…”