ABSTRACT
A novel organo sulfur and selenium-controlled emission behavior in discrete copper(I) clusters has been demonstrated for the first time. The pentanuclear [Cu5Br5(L1)2] (1), trinuclear [Cu3Br3(L2)2] (2), dinuclear [Cu2I2(L1)2] (3), and tetranuclear [Cu4I4(L2)2CH3CN] (4) copper(I) discrete clusters have been synthesized from the reaction between L1 [L1 = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-thione] or L2 [L2 = 1-isopropyl-3-(pyridin-2-yl)-imidazol-2-selone] chelating ligands and corresponding copper(I) halide salts. These new clusters have been characterized by FT-IR, UV-visible, thermogravimetric analysis, and fluorescence spectroscopy techniques. Single-crystal X-ray diffraction studies reveal that 1-4 consists of abundant d10-d10 interactions. The structural and bonding features of clusters have been investigated using density functional theory calculations. Notably, the L2-ligated 2 and 4 are poorly emissive, while L1-ligated 1 and 3 showed strong emission in the orange and green regions, respectively. The time-dependent density functional theory natural transition orbital calculations of 1 and 3 reveal the nature of the transitions contributed by 3MLCT/3LLCT/3ILCT. Photoluminescence quantum yields of 1 and 3 are 19 and 11%, with average lifetimes of 21.55 and 6.57 µs, respectively. 1 and 3 were coated on prototype LED bulbs for light-emitting performance.
ABSTRACT
The first discrete seven-membered cyclic zinc(II) complex catalyzed room temperature Knoevenagel condensation reactions, and the synthesis of perimidine derivatives has been reported under mild reaction conditions. The cyclic zinc(II) complex [(L)ZnBr2 ] (1) was isolated from the reaction between 1-(2-hydroxyethyl)-3-isopropyl-benzimidazol-2-thione (L) and ZnBr2 . Complex 1 was characterized by different analytic techniques such as FT-IR, CHNS, TGA, NMR, and SCXRD. The mononuclear zinc(II) complex 1 was utilized as a catalyst for Knoevenagel condensation reactions to isolate twenty different substituted methylene malononitriles with excellent yield. Besides, the zinc(II) thione complex 1 was utilized for the synthesis of 2,4-dihydroperimidine derivatives in a highly efficient manner. Catalyst 1 depicted wide substrate scopes. Overall, twenty different substituted methylene malononitriles and nine different perimidine derivatives were synthesized using catalyst 1 at room temperature. The present investigation features a mild and fast synthetic approach along with excellent functional group tolerance.
