Photochemical multivariate curve resolution models for the investigation of photochromic systems under continuous irradiation

• Published in: Analytica chimica acta Vol. 1053; pp. 32 - 42
• Main Authors: Devos, O., Schröder, H., Sliwa, M., Placial, J.P., Neymeyr, K., Métivier, R., Ruckebusch, C.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 11.04.2019; Elsevier BV; Elsevier Masson
• Subjects: Chemical Sciences; Constraint modelling; Ethene; Hard–soft modelling; Irradiation; Multivariate curve resolution; Parameter ambiguity; Photochemical reaction; Photochemicals; Photochromism; Quantum yield; Spectroscopy; Wavelengths; Parameter ambiguity; Photochemical reaction; Quantum yield; Multivariate curve resolution; Hard–soft modelling
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2018.12.004

We propose a multivariate curve resolution approach for the investigation of photochromic systems using UV-Visible spectroscopy. The incorporation of photochemical hard-models as constraints in multivariate curve resolution alternating least squares (MCR-ALS) allows extracting reaction quantum yields in situations where a complete knowledge of the system is not available. We apply this approach to the study of the photochromism of CMTE (cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene) under continuous monochromatic irradiation. The mechanism, involving 3 species and 2 reversible reactions, is written and translated into a kinetic constraint that can be applied to the concentration profiles within ALS. First, ambiguity of the solution obtained for photochemical model(s) is calculated and discussed for single set analysis. Multiset analysis is then proposed combining data obtained under different irradiation wavelengths to provide more reliable results. Finally, the photochemical reactivity of CMTE is widely unraveled, and some description of the mechanism observed under irradiation at 365 nm is given. [Display omitted] •Photochemical models have been implemented in MCR-ALS.•Ambiguities due to the photochemical model are calculated and the set of feasible quantum yields have been obtained.•Multiset hybrid hard-soft method has been applied to describe the photoreactions of a complex photochemical system.