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We investigated the photoinduced relaxation of Kasha-type emitting ruthenium-(bidentate cyclometalated aromatic ligand), Ru-CM, chromophores of [Ru(pzpy) 2 (CM)] + ions (CM = 1-phenylisoquinoline, 2,3-diphenylpyrazine, and 1,4-diazatriphenylene and pzpy = 2-pyrazol-1-yl-pyridine). This is the first report of the phosphorescence behavior of pure Ru-(bidentate CM) chromophores. The 77 K photoinduced relaxation characteristics of phosphorescence chromophores showed emission quantum yields higher than those of reference Ru-bpy (bpy = 2,2'-bipyridine) chromophores in the emission region of 670-900 nm. This phenomenon of the Ru-CM chromophores could be attributed to their unusually low magnitudes for 77 K nonradiative rate constants ( k NRD ), although their radiative rate-constants ( k RAD ) are not remarkable. In order to examine the 77 K photoinduced behavioral relaxation difference between Ru-CM and Ru-bpy chromophores, we used computational simulation, applying the fundamental formalism of k RAD and temperature-independent k NRD equations, which included calculated spin-orbit coupling values.

Three hitherto unknown eight-electron rhodium/silver alloy nanoclusters, [RhAg 21 {S 2 P(O n Pr) 2 } 12 ] ( 1 ), [RhHAg 20 {S 2 P(O n Pr) 2 } 12 ] ( 2 ), and [RhH 2 Ag 19 {S 2 P(O n Pr) 2 } 12 ] ( 3 ), have been isolated and fully characterized. Cluster 1 contains a regular Rh@Ag 12 icosahedral core, whereas 2 and 3 exhibit distorted RhH@Ag 12 and RhH 2 @Ag 12 icosahedral cores. The single-crystal neutron structure of 2 located the encapsulated hydride at the center of an enlarged RhAg 3 tetrahedron. A similar position was found by neutron diffraction for one of the hydrides in 3 , whereas the other hydride is trigonally coordinated to Rh and an elongated Ag-Ag edge. The solid-state structures of 1 - 3 possess C 1 symmetry due to the asymmetric arrangement of the surrounding capping Ag atoms. Our investigation shows that the insertion of one hydride dopant provokes the elimination of one capping silver atom on the cluster surface, resulting in the general formula [RhH x @Ag 21- x {S 2 P(O n Pr) 2 } 12 ] ( x = 0-2), which maintains the same number of cluster electrons as well as neutral charge. Clusters 1 - 3 exhibit an intense emission band in the NIR region. Contrarily to their PdAg 21 and PdHAg 20 relatives, the 4d orbitals of the encapsulated heterometal are somewhat involved in the optical processes.

The synthesis, electrochemistry, and photophysical characterization of five 2,2':6',2″-terpyridine ruthenium complexes (Ru-tpy complexes) is reported. The electrochemical and photophysical behavior varied depending on the ligands, i.e., amine (NH 3 ), acetonitrile (AN), and bis(pyrazolyl)methane (bpm), for this series of Ru-tpy complexes. The target [Ru(tpy)(AN) 3 ] 2+ and [Ru(tpy)(bpm)(AN)] 2+ complexes were found to have low-emission quantum yields in low-temperature observations. To better understand this phenomenon, density functional theory (DFT) calculations were performed to simulate the singlet ground state (S 0 ), T e , and metal-centered excited states ( 3 MC) of these complexes. The calculated energy barriers between T e and the low-lying 3 MC state for [Ru(tpy)(AN) 3 ] 2+ and [Ru(tpy)(bpm)(AN)] 2+ provided clear evidence in support of their emitting state decay behavior. Developing a knowledge of the underlying photophysics of these Ru-tpy complexes will allow new complexes to be designed for use in photophysical and photochemical applications in the future., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)