Luminescence quenching of Re(i) molecular rectangles by quinones

Abstract

The rhenium-based rectangles [{Re(CO)(3)(mu-bpy)Br}{Re(CO)(3)(mu-L)Br}](2) (I, L = 4,4'-dipyridylacetylene (dpa); II, L = 4,4'-dipyridylbutadiyne (dpb); III, L = 1,4-bis(4'-pyridylethynyl)benzene (bpeb); bpy = 4,4'-bipyridine) are emissive in solution at room temperature. The presence of extended pi conjugation leads to an increase in electron delocalization, which, in turn, results in improved luminescence and lower nuclear reorganization energy. These rectangles, upon electronic excitation, undergo facile electron transfer (ET) reactions with quinones and both the dynamic and static quenching contribute to the reaction. Spectral and electrochemical measurements show that quinone 7,7,8,8-tetracyanoquinodimethane (TCNQ) binds strongly to rectangle I. The driving force dependence of k(et), deduced from the luminescence quenching of rectangles with quinones, can be well accounted for within the context of the Marcus theory of electron transfer.

Phosphorescence “Turn‐On” Sensing of Anions by Rhenium(I) Schiff‐Base Complexes

“…Re(I)‐tricarbonyl diimine complexes are one of the most important and widely studied classes of luminescent d 6 transition metal complexes . The rich photophysical and photochemical behavior of the excited state rhenium(I)‐tricarbonyl complexes led to a wide range of interesting and important applications, including their use as sensors,, catalysts, light‐emitting devices, in CO 2 fixation, electron transfer, energy transfer, optical switches,, bioprobes,, and cellular imaging . The combination of photoactive metal center along with ligand is a desirable candidates for sensing anions.…”

A Dual Threat: Redox‐Activity and Electronic Structures of Well‐Defined Donor–Acceptor Fulleretic Covalent‐Organic Materials

“…Comparison of the acquired CV data for TCNQ[ 1≡(34 %) ] to TCNQ itself, shows that both potentials of TCNQ[ 1≡(34 %) ] are less negative at E p =−0.3 V and 0.2 V vs. SCE (Scheme ), which could be evidence of the stronger electron accepting properties of the prepared material. Thus, inclusion of TCNQ in a COF matrix affects the redox potential, which enables this compound to be electrochemically sensed . In comparison with C 60 itself which exhibits four quasireversible reductions at E p =−0.3 V, −0.7 V, −1.4 V, and −1.9 V in DMF vs. SCE, the NEM‐C 60 shows similar redox features at E p =−0.9 V and −1.8 V (Supporting Information, Figures S18 and S20).…”

“…Such electrochemical behavior (namely, presence of two waves in the cyclic voltammogram) is comparable with C 60 ‐based dimers in the literature, with a reduced symmetry comparable to NEM‐C 60 . While CVs with integrated acceptors have been measured for other systems such as molecular rectangles, these are the first studies, to the best of our knowledge, that demonstrate redox‐active behavior of TCNQ‐ and C 60 ‐integrated COFs.…”

Synthesis and Photophysical Properties of Rhenium(I)-Alkynyl Molecular Rectangles

“…Compounds 1, 4-bis(4'-pyridylethynyl)benzene (bpeb), 1,4-bis (4'-pyridylethynyl)naphthalene (bpen) and 1,4-bis (4'-pyr idylethynyl)anthracene (bpea) were synthesized by published methods [16][17][18] . The details of the synthesis of 1 have already been published 19,20 .…”