Green Phosphorescent Zn(II) Halide Complexes with N,N,N′,N′‐tetramethyl‐P‐indol‐1‐ylphosphonic Diamide as Ligand

• Published in: European journal of inorganic chemistry 2022-06, Vol.2022 (16), p.n/a
• Main Authors: Ferraro, Valentina, Baggio, Filippo, Castro, Jesús, Bortoluzzi, Marco
• Format: Article
• Language: English
• Subjects: [O=P]-donor ligands; Coordination compounds; Crystal structure; Emission; Excitation; Indole; Inorganic chemistry; Ligands; Luminescence; Phosphorescence; Zinc(II)
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202200119

Tetrahedral Zn(II) complexes having general formula [ZnX2{O=P(NMe2)2Ind}2] (X=Cl, Br, I, NCS) were isolated from the reaction between the indol‐1‐yl substituted phosphoramide N,N,N′,N′‐tetramethyl‐P‐indol‐1‐ylphosphonic diamide O=P(NMe2)2Ind and anhydrous Zn(II) precursors under mild conditions. The structures of the three halide derivatives were ascertained by single‐crystal X‐ray diffraction. The bromo‐ and iodo‐derivatives revealed to be appreciably luminescent in the green region upon excitation with light below 300 nm, with emission bands centred between 520 and 530 nm. The large Stokes shifts and the excited state lifetimes in the milliseconds range indicated that triplet excited states are involved in the emission. TD‐DFT calculations indicated that the luminescence is related to a ligand‐centred transition with the involvement of triplet states. Tetrahedral Zn(II) complexes with indolyl‐substituted phosphoramides and heavy halides in the coordination sphere showed appreciable photoluminescence in the visible range upon excitation with UV light. Experimental and computational data indicate that the emissions are associated to ligand‐centred triplet states.