Spectroscopic properties of macrocyclic oligo(phenyldiacetylenes)-II. Synthesis and theoretical study of diacetylenic dehydrobenzoannulene derivatives with weak electron-donor and -acceptor groups

Abstract

Diacetylenic dehydrobenzo [12]annulene and dehydrobenzo [18]annulene derivatives with electron-donor and -acceptor groups were synthesized (including push-pull Eglinton-Galbraith dimer derivative 1c) via an oxidative coupling reaction, and spectroscopically and structurally characterized. The solid-solid phase transition in 1b has been revealed at 45 8C by DSC measurements. Its room temperature crystal structure has been solved by X-ray diffraction measurements. The 1 H and 13 C NMR chemical shifts, UV/vis and infrared absorption spectra and Raman scattering spectra have been analyzed by using ground-state DFT calculations. The strongest absorptions in the UV/vis spectra of 1 and 2 most probably are not due to the HOMO/LUMO excitations but due to the (HOMO-1)/LUMO and HOMO/(LUMOC1) excitations. The substitution effects on the electronic charge distribution of the all-carbon annulenic cores can be particularly well observed in the distribution of IR intensities in the region of acetylenic stretching vibrations. IR intensities are thus useful in studying the extent of resonance interactions also in acetylenic macrocycles.

Intensified C≡C Stretching Vibrator and Its Potential Role in Monitoring Ultrafast Energy Transfer in 2D Carbon Material by Nonlinear Vibrational Spectroscopy

“…The vibrational frequency of a given normal mode, which is essentially composed of chemical groups, can be affected by many intra- and intermolecular interactions, particularly conjugation and hybridization effects. Previous infrared vibrational studies of the carbon–carbon triple bond (CC) , showed that the CC stretching mode in the form of R–CC–R′ is usually IR-inactive if R and R′ are identical and nonaromatic chemical groups. If R and R′ are different hydrocarbon groups, the CC stretching mode becomes weakly IR-active, with a molecular absorption coefficient being even smaller than the C–H group .…”

Determination of Phase Transition Temperatures by the Analysis of Baseline Variations in Transmittance Infrared Spectroscopy

“…10) are in good agreement with previous DSC measurements. 6,12,13 The exothermic DPB polymerization (120 kJ mol À1 ) is visible in the thermogram at 190 8C, with peak maximum at 240 8C, and analogous behavior is present in the baseline variations of DPB. The decomposition of macrocycles 1 and 2 is an extremely exothermic process.…”

“…Benzoannulenic macrocycles (octadehydrodibenzo [12]annulenes 1, and dodecadehydrotribenzo[18]annulenes 2) were synthesized by Swager's method as previously reported. 5,6 Temperature-dependent behavior of pellets made only of KBr was also measured. They showed linear temperature dependence of absorbance in the 4000-400 cm À1 range at any chosen wavenumber (with average R 2 ¼ 0.994).…”

Exploring Crystal Structure in Ethyne‐Substituted Pentacenes, and Their Elaboration into Crystalline Dehydro[18]annulenes

“…500 nm, likely arising from the annulene chromophore red-shifted by the appended pentacenes. [28] While reasonably stable in the solid state, manipulations of solutions of these DHAs were performed with shielding from laboratory light. Even relatively dilute solutions shielded from oxygen showed a half-life of approximately 18 hours (as determined by UV/Vis absorption studies -see Figure S2 in the Supplementary Information).…”