Synthesis and optical and nonlinear optical properties of linear and two-dimensional charge transfer chromophores based on polyoxometalates

Hood, Bethany R., de Coene, Yovan, Jones, Claire F., Lopez Poves, Ivan, Deveaux, Noah, Halcovitch, Nathan R., Champagne, Benoit, Clays, Koen and Fielden, John (2024) Synthesis and optical and nonlinear optical properties of linear and two-dimensional charge transfer chromophores based on polyoxometalates. Inorganic Chemistry, 63 (51). 24250–24261. ISSN 0020-1669

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Abstract

We present the first study of arylimido-polyoxometalate nonlinear optical (NLO) chromophores with two-dimensional (2D) structures, and a comparison with one-dimensional analogues, through the synthesis of a family of arylimido-hexamolybdate derivatives where one or two polyoxometalate (POM) acceptors are connected to a tolyl-amino donor through phenyl bridges. Electronic absorption spectra and TD-DFT calculations reveal significant red-shifts in ligand-to-polyoxometalate charge transfer (LPCT) absorption bands for the 2D species compared to linear, dipolar analogues, consistent with the involvement of a larger conjugated (bridge + POM) system in the transitions. Electrochemical measurements indicate reversible, one-electron processes for the POM acceptors with class II mixed valence behavior observed where the POMs are connected to the same aryl ring and electronic isolation of the acceptors when they are on separate rings. Molecular first hyperpolarizabilities β have been determined using hyper-Rayleigh scattering at 1064 and 1200 nm: for the most active compound, the HRS measurements and depolarization studies reveal a strongly 2D, off-diagonal response (β0,zzz = 190 × 10–30 esu; β0,zyy = −56.5 × 10–30 esu), consistent with the wide A–D–A angle and TD-DFT computed electronic transitions, which show both phenyl bridges and POMs equally involved in the acceptor orbitals.

Item Type:	Article
Additional Information:	Acknowledgments: We thank the EPSRC for support through grant EP/M00452X/1 to J.F., X-ray data were obtained in facilities established by EPSRC grant EP/S005854/1. B.R.H. thanks the University of East Anglia for a studentship and Lancaster University for short-term postdoctoral support. C.F.J. and J.F. acknowledge funding from the Leverhulme Trust (RPG-2020-365). Y.D.C. acknowledges the Fonds Wetenschappelijk Onderzoek (FWO) for senior postdoc (no. 1268825N). Calculations were performed on the UEA High Performance Cluster, Consortium des Équipements de Calcul Intensif (CECI, http://www.ceci-hpc.be), and the Technological Platform of High-Performance Computing, for which the authors acknowledge the financial support of the FNRS-FRFC, the Walloon Region, and University of Namur (Conventions No. GEQ U.G006.15, U.G018.19, U.G011.22, RW1610468, RW/GEQ2016, RW1117545, and RW2110213).
Faculty \ School:	Faculty of Science > School of Chemistry (former - to 2024) Faculty of Science > School of Chemistry, Pharmacy and Pharmacology Faculty of Science
Depositing User:	LivePure Connector
Date Deposited:	09 May 2025 16:30
Last Modified:	11 May 2025 06:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/99235
DOI:	10.1021/acs.inorgchem.4c04179

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