Unique interplay between electronic states and dihedral angle for the molecular rotor diphenyldiacetylene

• Published in: Physical chemistry chemical physics : PCCP Vol. 13; no. 36; pp. 16168 - 16174
• Main Authors: THULSTRUP, Peter W, HOFFMANN, Søren V, HANSEN, Bjarke K. V, SPANGET-LARSEN, Jens
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 28.09.2011
• Subjects: Absorption spectra; Chemistry; Dichroism; Exact sciences and technology; General and physical chemistry; Mathematical analysis; Polyethylenes; Quantum chemistry; Rotors; Spectroscopy; Synchrotron radiation; Temperature distribution; Temperature dependence; Polyethylene; Support; Conformational dynamics; Theoretical study; Equilibrium; Absorption spectrum; Optical properties; Dichroism; Density functional method; Synchrotron radiation; Chromophore
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c0cp02914a

A new analysis of the optical properties of the molecular rotor 1,4-diphenyl-1,3-butadiyne (diphenyl-diacetylene, DPDA) is presented, taking account of the conformational dynamics. The absorption spectra are interpreted in terms of simultaneous contributions from planar as well as non-planar rotamers, characterized by a temperature dependent equilibrium distribution. The investigation is based on IR Linear Dichroism and UV Synchrotron Radiation Linear Dichroism (SRLD) spectroscopy on oriented samples in stretched polyethylene (PE), and on variable temperature UV spectroscopy. The study is supported by the results of detailed quantum chemical Time Dependent Density Functional Theory (TD-DFT) calculations. The resulting analysis has profound implications for the understanding of the optical, photochemical, and photophysical characteristics of this and related chromophores, of importance in a variety of applications.