Cyclohexene‐Embedded Dicyanomethylene Merocyanines – Consecutive Three‐Component Coupling‐Addition Synthesis and Chromophore Characteristics

• Published in: ChemistryOpen (Weinheim) Vol. 12; no. 9; pp. e202300128 - n/a
• Main Authors: Papadopoulos, Julian, Reiss, Guido J., Mayer, Bernhard, Müller, Thomas J. J.
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01-09-2023; John Wiley and Sons Inc; Wiley-VCH
• Subjects: Absorption spectra; Absorptivity; Alternations; Banded structure; Chromophores; Condensation; cross-coupling; Crystal structure; Cyclohexene; DFT calculations; Dyes; Electronic structure; merocyanines; Michael addition; Molecular orbitals; multicomponent reactions; Synthesis; Temperature
• ISSN: 2191-1363; 2191-1363
• DOI: 10.1002/open.202300128

A concise and efficient consecutive three‐component alkynylation‐addition synthesis of cyclohexene‐embedded dicyanomethylene merocyanines furnishes a small library of dyes in moderate to excellent yield. The dyes possess strong absorption coefficients of the longest wavelength absorption bands. According to the crystal structure, the small bond length alternations account for a highly delocalized electronic ground state. The electronic structure of the absorption bands is qualitatively rationalized by TDDFT calculations, which explain that intense HOMO‐LUMO transitions along the merocyanine axis lead to cyanine similar Stokes shifts.
A library of cyclohexene‐embedded dicyanomethylene merocyanines is efficiently obtained by a consecutive three‐component alkynylation‐addition synthesis in moderate to excellent yield. The dominant intense longest wavelength absorption bands can be assigned, by TDDFT calculations, as HOMO‐LUMO transitions along the merocyanine axis.