Session: Session 2

Characterization of a photocaged organocatalyst: from LC-ESI-MS/MS to MALDI-MS mass spectrometry

The photorelease of a chemical entity, often referred to as “photo-uncaging”, providing unidirectional and irreversible generation of chemical entities has been employed since the late 1970s as a tool for the control of biological processes and controlled release of bioactive substances.[1] This approach has been more recently extended to the development of efficient photoacid and photobase generators targeted towards polymeric materials and photoresist application, but the strategy in which an organocatalyst is released from a photoactive “cage” substrate has been surprisingly much less explored.[2],[3]

The objective of this study is to characterize the photochemical properties of new photocaged thiourea organocatalysts, designed to be active in a variety of chemical transformations with potential applications ranging from fine chemistry to material sciences.[4]

First, the photorelease of the thiourea catalyst was followed and optimized according to LC-ESI-MS/MS experiments. All these analyses were done using an Infinity II HPLC chain coupled to an ESI-Q-TOF (6540, Agilent) operated in positive and negative ion modes. Kinetic studies were performed by irradiating at 438 nm the photocaged thiourea for different times. Depending on the solvent and concentrations, we observed the release of an unexpected structurally altered catalyst.

Then, in the second part, photo-initiated polymerization experiments could be performed, and the polymers could be characterized by MALDI-TOF mass spectrometry. An Ultraflextrem MALDI-TOF/TOF instrument from Bruker Daltonics was used for these experiments.



[1]C. Brieke, F. Rohrbach, A. Gottschalk, G. Mayer, A. Heckel, Angew.Chem.Int.Ed.2012,51,8446.

[2]N. Zivic, P. K. Kuroishi, F. Dumur, D. Gigmes, A. P. Dove, H. Sardon, Angew.Chem.Int. Ed.2019,58,10410.

[3]L. Rocard, J. Hannedouche, N. Bogliotti, Chem. Eur. J. 2022, 28

[4]Z. Zhang, Z. Bao, H. Xing. Org. Biomol. Chem. 2014, 12, 3151. b) I. Jain, P.Malik,Eur.Polym.J.2020,133,109791.