New Y-type chromophores FTC-yh1 and FTC-yh2 containing bis(N,N-diethyl)aniline as a novel electron-donor, thiophene as a π-conjugated bridge and tricyanofuran (TCF) as an acceptor have been synthesized and systematically investigated in this paper. Density functional theory (DFT) was used to calculate the HOMO–LUMO energy gaps and first-order hyperpolarizability (β) of these chromophores. These chromophores showed better thermal stability with their decomposition temperatures all above 240 °C. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic (EO) coefficients (r33) in poled polymers. The doped film-A containing 25 wt% chromophore FTC-yh1 displayed a value of 149 pm V−1 at 1310 nm, and the doped film-B containing FTC-yh2 showed a value of 143 pm V−1 at the concentration of 25 wt%. These values are almost four times higher than the EO activity of usually reported traditional single (N,N-diethyl)aniline nonlinear optical (NLO) chromophores FTC. High r33 values indicated that the double donors of the bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and reduce intermolecular electrostatic interactions, thus enhancing the macroscopic EO activity. These properties, together with the good solubility, suggest the potential use of the new chromophores as advanced material devices.

Synthesis and optical nonlinear property of Y-type chromophores based on double-donor structures with excellent electro-optic activity

Three novel second order nonlinear optical chromophores based on julolidinyl donors and tricyanovinyldihydrofuran (TCF) acceptors linked together via modified pyrrole π-conjugation (chromophores A and B) or thiophene moieties (chromophore C) as the bridges have been synthesized and systematically characterized. In particular, the pyrrole moiety bridge has been modified with the electron withdrawing group (–Br, –NO2) substituted benzene ring. The introduction of side phenyl groups to chromophores A and B can increase the thermal and chemical stability and reduce dipole–dipole interactions so as to translate their hyperpolarizability (β) values into bulk EO performance more effectively than chromophore C. Moreover, DFT calculations suggested that the additional electron withdrawing groups in chromophores A and B could increase the β value compared to that of chromophore D without substituted phenyl groups, and they showed different influences on the solvatochromic behavior, thermal stability, and electro-optic activity of the chromophores. EO responses (r33 values) of guest–host polymers containing pyrrole-bridged chromophores were reported. Incorporation of chromophores A and B into APC provided large electro-optic coefficients of 86 and 128 pm V−1 at 1310 nm with a high loading of 30 wt%. Film-C/APC containing 25 wt% of chromophore C provides an EO coefficient of 98 pm V−1.

Nonlinear optical chromophores containing a novel pyrrole-based bridge: optimization of electro-optic activity and thermal stability by modifying the bridge

Five napthyridine-based fluorine-boron (BF2-napthyridine) conjugated compounds have been theoretically designed, and subsequently, their photophysical properties are investigated. The influence of electron-donating and electron-withdrawing groups attached with the N∧C∧O moiety of BF2-napthyridine molecule has been interpreted. The optoelectronic properties, including absorption spectra and emission spectra of the BF2-napthyridine derivatives are studied using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) based methods. Different characteristics, such as HOMO-LUMO gap, molecular orbital density, ionization potential, electron affinity, and reorganization energy for hole and electron, are calculated. All these molecules show excellent π-electron delocalization. TD-DFT results illustrate that the amine-substituted BF2-napthyridine derivative has the highest absorption and emission maxima; it also shows a maximum Stoke shift. These results are well-correlated with the structural parameters and calculated HOMO-LUMO gap. Moreover, it is found that introduction of an electron-donating group into the BF2-napthyridine complex improves the hole transport properties and provides useful clues in designing new materials for organic light emitting diodes (OLED). As a whole, this work demonstrates that electron-donating and electron-withdrawing groups in BF2 derivatives can extend their effectiveness toward designing of OLED materials, vitro cellular studies, ex vivo assays, and in vivo imaging agents.

Role of Electron-Donating and Electron-Withdrawing Groups in Tuning the Optoelectronic Properties of Difluoroboron-Napthyridine Analogues.

A DFT/TDDFT modelling of bithiophene azo chromophores for optoelectronic applications

Novel second-order nonlinear optical chromophores containing multi-heteroatoms in donor moiety: Design, synthesis, DFT studies and electro-optic activities

Triazenes are a unique class of polyazo compounds containing three consecutive nitrogen atoms in an acyclic arrangement and are promising NLO candidates. In the present work, a series of 15 donor-π-acceptor type vinyl coupled triazene derivatives (VCTDs) with different acceptors (−NO2, −CN, and −COOH) have been designed, and their structure, nonlinear response, and optoelectronic properties have been studied using density functional theory and time-dependent density functional theory methods. B3LYP/6-311g(d,p) optimized geometries of the designed candidates show delocalization from the acceptor to donor through a π-bridge. Molecular orbital composition analysis reveals that HOMO is stabilized by the π-bridge, whereas acceptors play a major role in the stabilization of LUMO. Among the three acceptors, nitro derivatives are found to be efficient NLO candidates, and tri- and di-substituted cyano and carboxylic acid derivatives also show reasonably good NLO response. The effect of solvation on these propertie...

Tuning nonlinear optical and optoelectronic properties of vinyl coupled triazene chromophores: a density functional theory and time-dependent density functional theory investigation

R22(8), a commonly occurring motif in organic crystals, has been examined here through ab initio and density functional theory (DFT) methods. The 11 R22(8) motifs reported by Allen et al. have been classified into five types; their structural features, hydrogen-bonding patterns and the kind of interactions stabilising these motifs have been studied. Results reveal that the electronegativity of donor atoms plays a major role in directing the hydrogen bonds, whereas their positions in the motif have been found to be less important. Quantum theory of atoms in molecules (QTAIM) and reduced density gradient-based non-covalent-interaction analyses have been used to understand the weak interactions between monomers. Homonuclear interactions within the motifs have been found to be stronger with higher covalent character at the bond critical points than heteronuclear interactions. In addition, a localised molecular orbital energy decomposition analysis (LMOEDA) has been accomplished to provide useful insight into ...

S. Angeline Vedha

Papers

Tuning nonlinear optical and optoelectronic properties of vinyl coupled triazene chromophores: a density functional theory and time-dependent density functional theory investigation

The nature of hydrogen bonding in R22(8) crystal motifs – a computational exploration