Synthesis and photoluminescence properties of rhenium(i) complexes based on 2,2′:6′,2′′-terpyridine derivatives with hole-transporting units

Abstract

Based on 2,2′:6′,2′′-terpyridine ligands (L1), five terpyridine derivatives, namely 4′-carbazol-9-yl-2,2′:6′,2′′-terpyridine (L2), 4′-diphenylamino-2,2′:6′,2′′-terpyridine (L3), 4′-bis(4-tert-butylphenyl)amino-2,2′:6′,2′′-terpyridine (L4), 4′-[naphthalen-1-yl-(phenyl)amino]-2,2′:6′,2′′-terpyridine (L5), 4′-[naphthalen-2-yl(phenyl)amino]-2,2′:6′,2′′-terpyridine (L6) and their corresponding Re(I) complexes ReL(n)(CO)3Cl (n = 1–6) have been synthesized and characterized by elemental analysis and 1H NMR spectroscopy. The X-ray crystal structure of ReL3(CO)3Cl has also been obtained. The luminescence spectra of ReL2(CO)3Cl–ReL5(CO)3Cl, obtained in CH2Cl2 solution at room temperature, show strong dπ (Re) → π* (diimine) MLCT character (λ(max) 600 nm) and a small red shift relative to ReL1(CO)3Cl. This, confirmed by the study of the triplet energy levels of the L1–L6 ligands at low temperature (77 K rigid matrix), indicates that the introduction of electron-donating moieties on the terpyridine unit decreases the triplet levels of the ligands, leading to a reduction of the energy gap between d and π* orbitals. In the solid state, upon MLCT excitation, all the complexes show an even stronger emission and a blue spectral shift (λ(max) ∼ 550 nm) compared to those obtained in solution.

Electronic Effects of Substituents on fac-M(bpy-R)(CO)3 (M = Mn, Re) Complexes for Homogeneous CO2 Electroreduction

“…The coordination bond of N1 is 0.1 Å longer than that of N2 (see Figure 1 for numeration) and a similar asymmetry can be observed in the coordination of CO in trans position to the nitrogens. This asymmetric coordination, also present in other terpyridine derivatives (Anderson et al, 1990; Civitello et al, 1993; Wang et al, 2013; Klemens et al, 2016) is completely different from the very symmetrically bonded bpy derivatives (with N-Re average distances equal in the two coordinating pyridyl rings and long 2.17 Å). At the same time, while most of the 2,2′-bipyridine derivatives of fac -Re(CO) 3 Cl complex unit are almost planar respect to the basal OC–Re–CO plane (Kurz et al, 2006; Smieja and Kubiak, 2010; Bullock et al, 2012; Machan et al, 2014; Manbeck et al, 2015), in the case of 2e and 2f , the ligand is distorted outside this plane (see Table 1).…”

The switching of a Rhenium(i) complex from turn-off to turn-on sensor system through protein binding

“…The absorption spectra of these complexes show strong absorption bands at 243-294 nm and less intense absorption shoulders at 350-390 nm. With reference to the previous studies on related Re(I) tricarbonyl polypyridyl complexes, [35][36][37][38][39] these high and low energy absorptions are assigned to ligand centered ( 1 IL) (p / p*) (N-N and pyridine ligands) and spin allowed metal to ligand charge transfer 1 MLCT (dp (Re) / p*(N-N)) transitions respectively. The lowest energy absorption band of the bipyridine complex (1a) (345 nm) occurs at higher energy than those of the phenanthroline complex (1b) (365 nm).…”

Luminescent properties, internal hydrogen bonds and π–π interactions of Cd(II), Zn(II), Co(II) complexes based on 2,8-di(pyridin-4-yl)dibenzothiophene and dicarboxylate ligands

“…Over the past two decades, coordination polymers are of great interest, not only because of their aesthetic structures [1][2][3], but also because of their potential applications in the fields of photochemical areas [4], gas adsorption and separation [5], molecular magnetism [6], heterogeneous catalysis [7], and nonlinear optics (NLO) [8]. As we know, all applications of coordination polymers are based on their internal microstructures.…”