Theoretical investigation of oligomer structure and optoelectronic properties for [4-(methoxyphenyl)acetonitrile]n (n=1-5).

Experimental measurement on oligomeric 4-(methoxyphenyl)acetonitrile (OMPA) synthesized via an electrochemical method indicated that the average chain length for OMPA was around 5 units (5-MPA) [J Mol Struct 1031:186 (2013)], but did not provide enough information to completely characterize the chemical structure of the molecule. Nevertheless a possible structure was proposed on the basis of 13C NMR and the spin density hypothesis for radical polymerization. A more complete validation of the resultant structure is needed to show the extent to which the structure is consistent with a variety of measured properties. This is done here for the infrared (IR), ultraviolet-visible (UV-vis), and photoluminescence (PL) spectra of 5-MPA which are found to agree reasonably well with the experimentally measured spectra of OMPA. Electronic structure information regarding the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) energies, ionization potentials and electron affinities, as well as optical properties (UV-vis, PL) is also provided. Graphical Abstract Comparison of theoretical and experimental UV-visible absorption and photoluminescence spectra of oligomeric 4-(methoxyphenyl)acetonitrile.

New bridged oligofuran for optoelectronic applications.

Based on density functional theory (DFT) calculations, we have investigated the structural and optoelectronic properties of oligofuran (OFu)-bridged systems via useful electron donating groups (>S, >CH2, >SiH2 and >NH) and electron accepting ones (>CC(CN)2, >CO, >CS and >CCH2). The results were then discussed and compared with those obtained with the correspondingunbridged form. It was found that the optical band gap of OFu decreases significantly when it is bridged by >NH group arranged through an alternating way with >CS or >CC(CN)2 group, which gives bridged polyfuran (PFu) with desirable opto-electronic properties. Further, an intra-molecular charge transfer for the systems was undertaken in support of time-dependent DFT (TD-DFT) and semi-empirical ZINDO calculations. In this frame, we have shown that >CC(CN)2 and >S bridging groups leads to a new oligomer possessing favorable optoelectronic parameter for its use as an active layer in organic photovoltaic cells.

Theoretical study of phenylene-thiophene oligomers: structure-properties relationship.

Theoretical results including geometrical characteristics, electronic structures, photophysical parameters (lowest excitation energies, electron affinities (EAs), ionization potentials (IPs), maximum of absorption and emission) and vibrational modes of some new oligomers, based on phenylene-thiophene motives, are investigated using Density Functional Theory DFT/B3LYP/6-31G(d) approach. The electronic and optical properties of phenylene-based derivatives can be tuned through the insertion of thiophene in the main oligomers backbone as well as the addition of alkoxy-substituent groups on 2 and 5 positions on phenylene groups. It can be noticed, that different conformational behaviors and steric effects take place. Then, an increase in conjugation length induces a decrease in the gaps energy and a bathochromic shift of absorption/emission spectra. Based on these computed results, which are consistent with the available experimental data, the correlation structure-properties is better understood, where these nanostructures show a great potential for opto-electronic devices.