Issue 21, 2024

Orthopalladated imidazolones and thiazolones: synthesis, photophysical properties and photochemical reactivity

Abstract

The reaction of Pd(OAc)2 with (Z)-5-arylidene-4-(4H)-imidazolones (2a–e) and (Z)-4-arylidene-5(4H)-thiazolones (3a–e) in trifluoroacetic acid results in the corresponding orthopalladated dinuclear complexes (4a–e, imidazolones; 11a–d, thiazolones) with trifluoroacetate bridges through regioselective C–H activation at the ortho position of the 4-arylidene group. Compound 4e, which contains an imidazolone substituted at 2- and 4-positions of the arylidene ring with methoxide groups and exhibits strong push–pull charge transfer, is an excellent precursor for the synthesis of fluorescent complexes with green yellowish emission and remarkable quantum yields. Breaking the bridging system with pyridine yields the mononuclear complex 5e (ΦF = 5%), while metathesis of trifluoroacetate ligands with chloride leads to the dinuclear complex 6e, also a precursor of fluorescent complexes by breaking the chloride bridging system with pyridine (7e, ΦF = 7%), or by substitution of chloride ligands with pyridine (8e, ΦF = 15%) or acetylacetonate (9e, ΦF = 2%). In addition to notable photophysical properties, dinuclear complexes 4 and 11 also exhibit significant photochemical reactivity. Thus, irradiation of orthopalladates 4a–c and 11a–c in CH2Cl2 with blue light (465 nm) proceeds via [2 + 2] photocycloaddition of the C[double bond, length as m-dash]C double bonds of imidazolone and thiazolone ligands, yielding the corresponding cyclobutane-bridging diaminotruxillic derivatives 10a–c and 12a–c, respectively.

Graphical abstract: Orthopalladated imidazolones and thiazolones: synthesis, photophysical properties and photochemical reactivity

Supplementary files

Article information

Article type
Paper
Submitted
11 мар 2024
Accepted
01 май 2024
First published
02 май 2024
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2024,53, 8948-8957

Orthopalladated imidazolones and thiazolones: synthesis, photophysical properties and photochemical reactivity

D. Dumitraş, D. Dalmau, P. García-Orduña, A. Pop, A. Silvestru and E. P. Urriolabeitia, Dalton Trans., 2024, 53, 8948 DOI: 10.1039/D4DT00730A

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