The influence of structural isomerism on luminescence properties of [Re(CO)2(dppv)(pbi)] complexes containing cis-1,2-bis(diphenylphosphino)-ethene and 2-(2-pyridyl)benzimidazole ligands

Abstract

Simple reaction procedure, boiling of an equimolar mixture of [Re(Cl)(CO)3(dppv)] (dppv—cis-1,2-bis(diphenylphosphino)-ethene), 2-(2-pyridyl)benzimidazole (pbi), and TlClO4 in o-dichlorobenzene solution, leads to two, chromatographically separable, isomers of [Re(CO)2(dppv)(pbi)] complex. The obtained species, the yellow-emissive [OC-6–54] and the orange-emissive [OC-6–53] isomers, have been identified using FT-IR, 1H NMR, and 31P NMR spectroscopy and their structures confirmed by means of X-ray investigations. According to obtained crystallography results, the investigated isomers differ mainly in the arrangement of the 2-(2-pyridyl)benzimidazole anion in their structures. Diverse arrangement of the dppv and pbi ligand around the central cis-[Re(CO)2]+ core results in well-pronounced changes in luminescence properties of the studied luminophores. According to results from performed DFT and TDA-DFT computations, the [OC-6–54] isomer emission occurs from the intra-ligand excitation localized mainly within the pbi ligand. In contrary to that, the [OC-6–53] isomer emission indicates some metal-to-ligand charge-transfer character associated with the charge transfer from the Re(CO)2(dppv)+ fragment to the pbi ligand. Moreover, both isomers exhibit different character of their emission decays, mono-exponential and bi-exponential for the [OC-6–54] and [OC-6–53] ones, respectively. In the view of obtained DFT/TDA-DFT results, this has been explained by the presence of an additional excited dark state, operative only in the case of the [OC-6–53] isomer and associated with the charge transfer from the Re(CO)2(pbi) fragment to the dppv ligand.

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…the ability of compounds with identical molecular formulae to exist in spatially different forms is one of the most fundamental ideas in chemistry. [1][2][3] Revealing the impact of isomerism on crystal structures, [4][5][6][7][8][9][10][11][12] and chemical properties, [13][14][15][16][17][18][19][20][21] as well as physical [22][23][24][25][26][27][28][29][30][31][32][33][34] and biological properties [35][36][37][38][39] is of particular importance for establishing structure-property relationships which pave the way toward the more predictable design of substances with desirable properties. Despite various kinds of constitutional and configurational isomerism of metal complexes being well known, 40 ligand isomerism, which belongs to constitutional isomerism, is documented in literature to a considerably lesser extent than other types of the isomerism of complexes.…”