Tuning Optical Properties of Re(I) Carbonyl Complexes by Modifying Push–Pull Ligands Structure

Abstract

In this work, the structure–property relationship was investigated for a series of Re­(I) carbonyls [ReCl­(CO)3(R-terpy-κ2N)], [ReCl­(CO)3(R-dtpy-κ2N)], and [ReCl­(CO)3(R-dppy-κ2N)]. The studied compounds bear 2,2′:6′,2″-terpyridines (R-terpy), 2,6-di­(thiazol-2-yl)­pyridines (R-dtpy), and 2,6-di­(pyrazin-2-yl)­pyridines (R-dppy) functionalized with strongly electron-donating cyclic (piperidine and morpholine) and acyclic (dimethylamine, diphenylamine) amine donor attached to the central pyridine ring of the triimine skeleton via phenylene linkage. Their thermal properties were evaluated using DSC. The ground- and excited-state properties of these systems were elucidated with electrochemistry, absorption and emission spectroscopy, and density-functional theory (DFT)-based calculations. The terpy skeleton was found to efficiently stabilize the LUMO orbital, as manifested by the most negative reduction potentials for Re­(I) terpyridine complexes and significant blue-shift of the absorption and emission of [ReCl­(CO)3(R-terpy-κ2N)] in relation to those of Re­(I) carbonyls bearing dtpy- and dppy-based ligands. Substitution of the triimines with amine substituents resulted in participation of intraligand charge-transfer (ILCT) transitions, and it was found to be beneficial for hole-transport properties of the Re­(I) carbonyls. The constructed nondoped and doped single layer diodes based on Re­(I) complexes emitted red light with various intensity.

In-Depth Studies of Ground- and Excited-State Properties of Re(I) Carbonyl Complexes Bearing 2,2′:6′,2″-Terpyridine and 2,6-Bis(pyrazin-2-yl)pyridine Coupled with π-Conjugated Aryl Chromophores

“… 20 Prolonged lifetimes have also been confirmed for some Re(I) diamine carbonyls [ReX(CO) 3 (phen-TPA)] (X = Cl, Br; TPA = triphenylamine) with the emitting state of 3 ILCT nature, 21 and they have been supported for some other terpyridine Re(I) complexes [ReCl(CO) 3 (L n -κ 2 N )] incorporating strong electron-donating substituents by the Wang group 22 and our group. 14 , 16 , 23 …”

“…Most of the Re­(I) carbonyl complexes [ReCl­(CO) 3 (L n -κ 2 N )] bearing substituted terpy-like ligands coordinated to the metal center in a bidentate way that have been developed so far − emit from the triplet excited state of metal to ligand charge-transfer character ( 3 MLCT). Generally, they are weakly emissive at room temperature and have short excited-state lifetimes.…”

The role of substituted pyridine Schiff bases as ancillary ligands in the optical properties of a new series of fac-rhenium(i) tricarbonyl complexes: a theoretical view

“…10,17,19 A particular combination of ligands can affect the metalcore due to their donor or acceptor properties. [20][21][22][23][24] Interestingly, ligands choice affects the photophysical properties and impacts the biological effect, such as therapeutical applications or antimicrobial properties, including protein stain. 18,25,26 Over the last few years, luminescent Re(I) tricarbonyl complexes have been increasingly proposed as uorophores suitable for uorescence microscopy to visualize biological structures and cells.…”

Targeted Synthesis of NIR Luminescent Rhenium Diimine cis,trans‐[Re()(CO)2(L)2]n+ Complexes Containing N‐Donor Axial Ligands: Photophysical, Electrochemical, and Theoretical Studies

“…In room temperature solution the most part of the known complexes display emission in the visible area of spectrum. Much smaller number of compounds of this type show emission band maxima in the 700–780 nm range [13,27,59–62] . To the best of our knowledge, the rhenium complexes with emission maxima below 790 are not known.…”

“…Much smaller number of compounds of this type show emission band maxima in the 700-780 nm range. [13,27,[59][60][61][62] To the best of our knowledge, the rhenium complexes with emission maxima below 790 are not known. Thus, λ em > 800 nm observed for the complexes 2Re(Py) 2 and (BiPy) 2 are the record values, which have been achieved by insertion of two pyridine donor ligands into axial positions of the rhenium coordination octahedron.…”