In Search of the Perfect Photocage: Structure-Reactivity Relationships in meso-Methyl BODIPY Photoremovable Protecting Groups

Tomáš Slanina, Pradeep Shrestha, Eduardo Palao, Dnyaneshwar Kand, Julie A. Peterson, Andrew S. Dutton, Naama Rubinstein, Roy Weinstain*, Arthur H. Winter, Petr Klán

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

176 Scopus citations

Abstract

A detailed investigation of the photophysical parameters and photochemical reactivity of meso-methyl BODIPY photoremovable protecting groups was accomplished through systematic variation of the leaving group (LG) and core substituents as well as substitutions at boron. Efficiencies of the LG release were evaluated using both steady-state and transient absorption spectroscopies as well as computational analyses to identify the optimal structural features. We find that the quantum yields for photorelease with this photocage are highly sensitive to substituent effects. In particular, we find that the quantum yields of photorelease are improved with derivatives with higher intersystem crossing quantum yields, which can be promoted by core heavy atoms. Moreover, release quantum yields are dramatically improved by boron alkylation, whereas alkylation in the meso-methyl position has no effect. Better LGs are released considerably more efficiently than poorer LGs. We find that these substituent effects are additive, for example, a 2,6-diiodo-B-dimethyl BODIPY photocage features quantum yields of 28% for the mediocre LG acetate and a 95% quantum yield of release for chloride. The high chemical and quantum yields combined with the outstanding absorption properties of BODIPY dyes lead to photocages with uncaging cross sections over 10 000 M-1 cm-1, values that surpass cross sections of related photocages absorbing visible light. These new photocages, which absorb strongly near the second harmonic of an Nd:YAG laser (532 nm), hold promise for manipulating and interrogating biological and material systems with the high spatiotemporal control provided by pulsed laser irradiation, while avoiding the phototoxicity problems encountered with many UV-absorbing photocages. More generally, the insights gained from this structure-reactivity relationship may aid in the development of new highly efficient photoreactions.

Original languageEnglish
Pages (from-to)15168-15175
Number of pages8
JournalJournal of the American Chemical Society
Volume139
Issue number42
DOIs
StatePublished - 25 Oct 2017

Funding

FundersFunder number
European Research Committee
National Science FoundationCHE-1464956
U.S. Department of EnergyDESC0014038
American Cancer SocietyACI-1053575, PRF55820-ND4
Horizon 2020 Framework Programme679189
Nadace Experientia
German-Israeli Foundation for Scientific Research and DevelopmentI-2387-302.5/2015
Ministerstvo Školství, Mládeže a TělovýchovyLM2011028, LO1214
Grantová Agentura České RepublikyGA13-25775S
Council for Higher Education
Chulabhorn Research Institute1205413
Medical Research Institute Sri LankaCBS 1229081

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