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The article studies the migration of acyl group in different photophysical and photochemical processes. Acyl group substitution is also found to largely affect the rate constants of these processes.

The infra red (IR) and ultra violet (UV)-vis spectroscopy were used to study the photochemical transformation of 1,3,2,4-benzodithiadiazine in argon matrices at 12 K. A series of intermediates, including four- and five- membered heterocyclic and o-quinoid acyclic species were characterized which could be mutually interconverted as well as converted back to the starting compound 1,3,2,4-benzodithiadiazine by selective irradiation.

A series of red-emissive {Cu4I6} clusters have been synthesized from alkyl-tris(2-pyridyl)phosphonium halides, [R-PPy3]Hal, and CuI. The size of the alkyl substituent (R) has a dramatic impact on the structure of the clusters assembled. [Me-PPy3]I salt reacts with CuI (1 : 2) to give the ionic [Cu(Me-PPy3)I]2Cu2I4 complex consisting of the scorpionate [Cu(N,N′,N′′-Me-PPy3)I]+ cation. Under similar conditions, [Pr-PPy3]I forms the zwitterionic [Cu4I6(Pr-TPP)2] complex containing an unusual stepwise [Cu4I6] cluster core. The use of [Bu-PPy3]I or [Bn-PPy3]I in this reaction leads to zwitterionic [Cu4I6(R-TPP)2] complexes, in which a linear-shaped [Cu4I6] module appears. Photophysical studies supported by TD-DFT computations have revealed that the title complexes in the solid state at 298 K exhibit a red photoluminescence (λemmax = 620–650 nm) with short lifetimes (0.04–2.10 μs), which are assigned to the thermally activated delayed fluorescence (TADF) mixed with the cluster centered (3CC) phosphorescence. The compounds synthesized are the first red-emitting representatives of the recently discovered family of zwitterionic CuI-based complexes (so-called “AIO” structures). [ABSTRACT FROM AUTHOR]

By means of cyclic voltammetry (CV) and DFT calculations, it was found that the electron‐acceptor ability of 2,1,3‐benzochalcogenadiazoles 1–3 (chalcogen: S, Se, and Te, respectively) increases with increasing atomic number of the chalcogen. This trend is nontrivial, since it contradicts the electronegativity and atomic electron affinity of the chalcogens. In contrast to radical anions (RAs) [1].− and [2].−, RA [3].− was not detected by EPR spectroscopy under CV conditions. Chemical reduction of 1–3 was performed and new thermally stable RA salts [K(THF)]+[2].− (8) and [K(18‐crown‐6)]+[2].− (9) were isolated in addition to known salt [K(THF)]+[1].− (7). On contact with air, RAs [1].− and [2].− underwent fast decomposition in solution with the formation of anions [ECN]−, which were isolated in the form of salts [K(18‐crown‐6)]+[ECN]− (10, E=S; 11, E=Se). In the case of 3, RA [3].− was detected by EPR spectroscopy as the first representative of tellurium–nitrogen π‐heterocyclic RAs but not isolated. Instead, salt [K(18‐crown‐6)]+2[3‐Te2]2− (12) featuring a new anionic complex with coordinate Te−Te bond was obtained. On contact with air, salt 12 transformed into salt [K(18‐crown‐6)]+2[3‐Te4‐3]2− (13) containing an anionic complex with two coordinate Te−Te bonds. The structures of 8–13 were confirmed by XRD, and the nature of the Te−Te coordinate bond in [3‐Te2]2− and [3‐Te4‐3]2− was studied by DFT calculations and QTAIM analysis. Heterocyclic radical anions: Chemical reduction of 2,1,3‐benzochalcogenadiazoles 1–3 (chalcogen=S, Se, Te, respectively) afforded new thermally stable radical anion (RA) salts [K(THF)]+[2].− and [K(18‐crown‐6)]+[2].− in addition to known salt [K(THF)]+[1].−, whereas RA [3].− was detected by EPR as the first Te–N π‐heterocyclic RA but not isolated; instead, salt [K(18‐crown‐6)]+2[3‐Te2]2− (12) featuring a new anionic complex with coordinate Te−Te bond was obtained (see figure). [ABSTRACT FROM AUTHOR]

To elucidate the multifaceted but pooly understood chemistry of the pivotal polysulfur-nitrogen heterocycle, tetrasulfur tetranitride (S4N4, 1), its photochemistry was studied in Ar matrices. Thereby two primary intermediates and a secondary one (2-4) were detected, and their UV-vis and IR spectra were identified throughspecific interconversions of 1-4 that can be induced by selective irradiations. The structures associated with these spectra were assigned with the help of OFT calculations. From these assignments it follows that, under the conditions of the present experiments, the cage structure of 1 transforms into isomeric structures 2-4, one of which is a boat-shaped 8-membered cycle (2), and the two other are novel 6-membered S3N3 cycles carrying exocyclic (N)-SN (3) or (S)-NS (4) groups, respectively, which have not been previously described. These three intermediates probably play a pivotal role in the formation of the diverse products that are observed in the reactions of S4N4 even under mild reaction conditions. [ABSTRACT FROM AUTHOR]

The bridged systems containing pyrenyl and aryl azido residues have been synthesized for the first time, and the quenching of pyrene fluorescence on a picosecond time scale has been observed. [Copyright &y& Elsevier]

The first example of a triply bridging (μ 3 -P) phosphine ligand has been discovered in the crown-shaped [Cu 3 (μ 2 -Hal) 3 L] (Hal=Cl, Br, or I) complexes supported by tris[2-(2-pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ 3 -P-bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s-orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λ em =442-465 nm) with the quantum efficiency reaching 100 %. The complex [Cu 3 (μ 2 -I) 3 L] also exhibits remarkable thermo- and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands., (© 2021 Wiley-VCH GmbH.)

A series of red-emissive {Cu4I6} clusters have been synthesized from alkyl-tris(2-pyridyl)phosphonium halides, [R-PPy3]Hal, and CuI. The size of the alkyl substituent (R) has a dramatic impact on the structure of the clusters assembled. [Me-PPy3]I salt reacts with CuI (1 : 2) to give the ionic [Cu(Me-PPy3)I]2Cu2I4 complex consisting of the scorpionate [Cu(N,N',N''-Me-PPy3)I]+ cation. Under similar conditions, [Pr-PPy3]I forms the zwitterionic [Cu4I6(Pr-TPP)2] complex containing an unusual stepwise [Cu4I6] cluster core. The use of [Bu-PPy3]I or [Bn-PPy3]I in this reaction leads to zwitterionic [Cu4I6(R-TPP)2] complexes, in which a linear-shaped [Cu4I6] module appears. Photophysical studies supported by TD-DFT computations have revealed that the title complexes in the solid state at 298 K exhibit a red photoluminescence (λemmax = 620-650 nm) with short lifetimes (0.04-2.10 μs), which are assigned to the thermally activated delayed fluorescence (TADF) mixed with the cluster centered (3CC) phosphorescence. The compounds synthesized are the first red-emitting representatives of the recently discovered family of zwitterionic CuI-based complexes (so-called "AIO" structures).