Solvent-modulated proton-coupled electron transfer in an iridium complex with an ESIPT ligand

Abstract

Proton-coupled electron transfer (PCET), an essential process in nature with a well-known example of photosynthesis, has recently been employed in metal complexes to improve energy conversion efficiency, but a profound...

Tuning ESIPT-coupled luminescence by expanding π-conjugation of a proton acceptor moiety in ESIPT-capable zinc(ii) complexes with 1-hydroxy-1H-imidazole-based ligands

“…To date, there are fewer than 30 references dealing with the synthesis and investigation of such complexes. 77–104 The ESIPT-capable ligands used for the synthesis of these complexes are various carboxylic acids (2,5-dihydroxyterepthalic acid, 3-hydroxy-2-quinoxalinecarboxylic acid), the derivatives of 2-(1 H -imidazol-2-yl)phenol, 1-(1 H -imidazo[4,5- f ][1,10]phenanthrolin-2-yl)naphthalen-2-ol, 77,78 4-(1 H -pyrazol-1-yl)-6-(2-hydroxyphenyl)pyrimidine 103,104 and 1-hydroxy-2-(pyridin-2-yl)-1 H -imidazole. 105,106 Whereas 2,5-dihydroxyterepthalic acid and the derivatives of 2-(1 H -imidazol-2-yl)phenol decorated with carboxylic groups are known to form metal–organic frameworks due to the coordination of the carboxylato groups to metal ions, other ligands feature N , N - and N , O -chelating metal binding sites which suit the formation of chelate complexes.…”

High-Performance Turn-On Fluorescent Metal–Organic Framework for Detecting Trace Water in Organic Solvents Based on the Excited-State Intramolecular Proton Transfer Mechanism

“…To overcome the existing obstacles, introducing the excited-state intramolecular proton transfer (ESIPT) process with huge luminescence Stokes shifts, ultrafast response, and light stability into MOFs may be an effective method to greatly improve the sensitivity and selectivity for water sensing. − After being stimulated by light, the ESIPT process can generate rapid intramolecular proton transfer between the hydrogen bond donors (−OH and −NH 2 ) and hydrogen bond acceptors (N– and CO) of the molecular structure via tautomerism from the excited enol form to keto form. − Based on this, 2,5-dihydroxyterephthalic acid (DHBDC) was selected to design LMOFs. DHBDC combines the abilities to construct stable MOFs and realize a high-efficiency ESIPT process originating from weak intramolecular H-bonds between two uncoordinated 2,5-hydroxyl groups and the chelate carboxylate oxygen. − The added water interacts with the −OH groups of DHBDC and affects the enol–keto tautomerism during the ESIPT process.…”

N-Hydroxy–N-oxide photoinduced tautomerization and excitation wavelength dependent luminescence of ESIPT-capable zinc(ii) complexes with a rationally designed 1-hydroxy-2,4-di(pyridin-2-yl)-1H-imidazole ESIPT-ligand

“…20 references. 38,66–88 For the most part, these complexes are based on aromatic carboxylic acids ( e.g. 3-hydroxy-2-quinoxalinecarboxylic acid, 2,5-dihydroxyterepthalic acid) and 2-(1 H -imidazol-2-yl)phenol derivatives decorated by aromatic carboxylic acid groups.…”

“…3-hydroxy-2-quinoxalinecarboxylic acid, 2,5-dihydroxyterepthalic acid) and 2-(1 H -imidazol-2-yl)phenol derivatives decorated by aromatic carboxylic acid groups. 66–88 Metal ions used in the synthesis of ESIPT-complexes are mostly the ions of divalent metals of the second and twelfth groups of the periodic table (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Zn 2+ , Cd 2+ ) and the ions of trivalent lanthanides (Sm 3+ , Eu 3+ , Tb 3+ , Gd 3+ , Er 3+ , Nd 3+ ). Metal–organic frameworks (MOFs) based on divalent ions show fluorescence.…”