title: Red to Near-Infrared Isoindole BODIPY Fluorophores: Synthesis, Crystal Structures, and Spectroscopic and Electrochemical Properties.
abstract: A series of high-performance fluorophores named isoindole boron dipyrromethenes (BODIPYs) containing either symmetrical or unsymmetrical alkyl substitution patterns on pyrrole rings were synthesized by an efficient process and were characterized by X-ray diffraction and spectroscopic and electrochemical analyses. Most of these dyes show strong, sharp absorption and bright fluorescence emission in the red to near-infrared (NIR) region (up to 805 nm in acetonitrile). Pyrrolic alkyl substitutions lead to increases in the HOMO and LUMO energy levels and an overall decrease in the energy band gaps of the dye. Among the 23 isoindole BODIPY dyes synthesized, solvent-dependent fluorescence emission and lifetime decay were only observed for those containing a 3-methyl substituent on the uncoordinated pyrrole ring, whereas little variation in the fluorescence intensity was observed for the rest of the dyes upon changing the polarity of the solvent. These resultant dyes can be further functionalized via the Knoevenagel condensation on the α-methyl substituent of the chromophore to install a variety of functionalities, including a dimethylamine group demonstrated in this work. This dimethylamine-functionalized isoindole BODIPY shows weak fluorescence at 805 nm in acetonitrile and a ratiometric "turn-on" NIR fluorescence response to decreasing pH.
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Changjiang
authors.initials: C
authors.lastname: Yu
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Wu
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Wei
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Erhong
authors.initials: E
authors.lastname: Hao
authors.affiliation: The Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, School of Chemistry and Materials Science, Anhui Normal University , Wuhu 241000, China.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Jiao