Silver(I) Complexes of Diphenylpyridines: Crystal Structures, Luminescence Studies, Theoretical Insights, and Biological Activities

Abstract

A series of simple two‐coordinated cationic silver(I) complexes, namely, [Ag{4‐(4‐R1‐phenyl)‐2,6‐diphenylpyridine}2]X (X=ClO4−, BF4−, or SO3CF3−), with different electron‐donating or ‐withdrawing groups (e.g., R1=N(Me)2, Me, H, Cl, and Br) on the phenyl ring, were successfully prepared. Extensive characterization of these complexes by various NMR spectroscopy techniques and mass spectrometry was further corroborated by single‐crystal XRD analyses. Detailed photophysical investigations of [Ag{4‐(4‐N,N‐dimethylaminophenyl)‐2,6‐diphenylpyridine}2]ClO4 (C1) displayed a strong room‐temperature fluorescence in solution with an anomalously high luminescence quantum yield of 0.83. The effects of distinct substituent groups (C2–C5), π‐conjugated aromatic rings (C6 and C7), and anions (C8 and C9) on the photoluminescence properties were evaluated. Furthermore, DFT and time‐dependent DFT calculations were performed to discern the composition of the excited state, as well as to confirm the obtained relative emission energies upon substitution with electronically different ligands. These results indicated that the strong electron‐donating substituent of N,N‐dimethylamine played an important role in the unprecedented high luminescence quantum yield of C1. In addition, preliminary antimicrobial studies and confocal microscopy fluorescent imaging of HeLa cells labeled with these complexes reveal their potential applications in biological activities.

0D to 3D Coordination Assemblies Engineered on Silver(I) Salts and 2‐(Alkylsulfanyl)azine Ligands: Crystal Structures, Dual Luminescence, and Cytotoxic Activity

“…Again, HE and LE emission of 2 and 3 could attribute to 1 IL and 3 IL transitions in the pyridine rings of the L1 ligand. In general, considering the previous studies, the dual emission is also typical for Ag (I) complexes containing N ‐heterocyclic ligands, as surely as pure intraligand phosphorescence, or fluorescence,, and thermally‐activated delayed fluorescence …”

Control of Emissive Excited States of Silver(I) Halogenido Coordination Polymers by a Solid Solution Approach

“…Monovalent Group 11 metal ions afford luminescent materials with a wide variety of ligands. − Extensive studies on strongly luminescent gold­(I) and copper­(I) complexes bearing ligands such as N-donors, − phosphines, − acetylides, − cyanides, , S-donors, − and carbenes − have been reported. Luminescent silver­(I) complexes with these ligands − have also been reported more recently. The excited states associated with the photoemission of these d 10 complexes include simple metal-centered, metal-to-ligand charge transfer (MLCT), and ligand-centered transitions.…”

Synthesis and Photophysical Properties of Emissive Silver(I) Halogenido Coordination Polymers Composed of {Ag2X2} Units Bridged by Pyrazine, Methylpyrazine, and Aminopyrazine

“…Compared to that of copper­(I) and gold­(I) complexes, the development of luminescent silver­(I) complexes has started only recently; however, several silver complexes exhibiting strong luminescence at room temperature, − thermally activated delayed fluorescence, − thermochromic luminescence, − and stimuli-responsive luminescence , have already been reported. Because the coordination properties and electronic structures of silver­(I) complexes are similar to those of copper­(I) complexes, the ligands affording luminescent copper­(I) complexes have also been exploited to synthesize luminescent silver­(I) complexes. ,− The obtained complexes typically display emission in the near-ultraviolet (UV) or blue region even though the corresponding copper­(I) complexes show colorful emission in the visible region. ,− Because the stability of the 4d orbitals of the silver­(I) center is higher than that of the 3d orbitals of the copper­(I) center, ,− the metal-to-ligand CT ES increases in energy, approaching those of the other ESs, which causes a mixing of the ESs and complicates their emissive ESs, hampering the rational design of a ligand set for luminescent silver­(I) complexes.…”