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The present study spotlights the hybrid chalcone derivatives consisting of coumarin moieties conjugated systematically with different heterocyclic rings. The heterocyclic rings including bifuran, bicyclopentane, bipyrrole and bithiophenes groups are used to design compounds 1 , 2 , 3 and 4 , respectively. Different density functional theory (DFT) methods are used for optimization of designed compounds. The M06 functional shows reasonably good accuracy for calculations of geometrical and absorption spectra as compared with other methods and/or available experimental data. The calculated average third-order NLO polarizabilities ( γ ) for compounds 1 , 2 , 3 and 4 are found to be 526.22 × 10 −36 , 675.40 × 10 −36 , 939.58 × 10 −36 and 1109.30 × 10 −36 esu., respectively, at M06/6-311G** level of theory. The γ amplitudes of compounds 1 , 2 , 3 and 4 are reasonably enhanced, which are about 25, 27, 30 and 32 times larger to the γ amplitude of para nitroaniline (a prototype NLO molecule) at same M06/6-311G** level of theory. Furthermore, we highlight the structure-property relationship using TD-DFT calculations for absorption and emission spectra, frontier molecular orbitals and molecular electrostatic potential maps. Thus, the present study will evoke the interest of scientific community to develop the above title materials for efficient NLO applications. [ABSTRACT FROM AUTHOR]

Using first-principle methods, several key electronic, optical and nonlinear optical properties are calculated for two recently synthesized chalcone derivatives i.e. (2E)-3-(4-methylphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (comp. 1 ) and (2E)-3-[4-(dimethylamino)phenyl]-1-(3-nitrophenyl)prop-2-en-1-one (comp. 2 ). The calculation of dipole moment, polarizability <α>, anisotropy of polarizability as well as second hyperpolarizability (usually considered as a signature for two photon absorption phenomenon) are performed using density functional theory methods at PBE0/6-311G** level of theory. The linear average polarizability <α> for comp. 1 and comp. 2 are found to be 32.15 × 10 −24 and 38.76 × 10 −24 esu, respectively. Similarly, the second hyperpolarizability <γ> amplitudes of comp. 1 and comp. 2 are found to be reasonably larger mounting to 79.31 × 10 −36 and 181.36 × 10 −36 esu, respectively. The importance of donor end is determined by comparing p -methylphenyl group of comp. 1 with that of N , N -dimethylaniline group of comp. 2 that results a remarkable increase in its <γ> amplitude, which is ∼2 times larger as compared with that of comp. 1 owing to the stronger donor-acceptor configuration of comp. 2 . Interestingly, a comparison of average static third-order nonlinear polarizabilities <γ> shows that <γ> amplitudes of comp. 1 and comp. 2 are ∼13 times and ∼29 times larger than that of para -nitroaniline (a typical standard push-pull NLO-phore) at the same PBE0/6-311G** level of theory, which indicates a real time NLO application of our titled compounds. Time dependent density functional theory (TD-DFT) calculations along with frontier molecular orbitals, density of states (DOS), second hyperpolarizability density analysis and molecular electrostatic potential (MEP) diagrams are used to trace the origin of electro-optical as well as structure property relationships. [ABSTRACT FROM AUTHOR]

Using the density functional theory methods, we effectively tune the second-order nonlinear optical (NLO) properties in some chalcone derivatives. Various unique push–pull configurations are used to efficiently enhance the intramolecular charge transfer process over the designed derivatives, which result in significantly larger amplitudes of the first hyperpolarizability as compared to their parent molecule. The ground state molecular geometries have been optimized using B3LYP/6-311G** level of theory. A variety of methods including B3LYP, CAM-B3LYP, PBE0, M06, BHandHLYP and MP2 are tested with 6-311G** basis set to calculate the first hyperpolarizability of parent system 1 . The results of M06 are found closer to highly correlated MP2 method, which has been selected to calculate static and frequency dependent first hyperpolarizability amplitudes of all selected systems. At M06/6-311G** level of theory, the permanent electronic dipole moment (μ tot ), polarizability (α 0 ) and static first hyperpolarizability (β tot ) amplitudes for parent system 1 are found to be 5.139 Debye, 274 a. u. and 24.22 × 10 −30 esu, respectively. These amplitudes have been significantly enhanced in designed derivatives 2 and 3 . More importantly, the (β tot ) amplitudes of systems 2 and 3 mount to 75.78 × 10 −30 and 128.51 × 10 −30 esu, respectively, which are about 3 times and 5 times larger than that of their parent system 1 . Additionally, we have extended the structure-NLO property relationship to several newly synthesized chalcone derivatives. Interestingly, the amplitudes of dynamic frequency dependent hyperpolarizability μβ ω (SHG) are also significantly larger having values of 366.72 × 10 −48 , 856.32 × 10 −48 and 1913.46 × 10 −48 esu for systems 1 – 3 , respectively, at 1400 nm of incident laser wavelength. The dispersion behavior over a wide range of change in wavelength has also been studied adopting a range of wavelength from 1907 to 544 nm. Thus, the present work realizes the potential of designed derivatives as efficient NLO-phores for modern NLO applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] New multifunctional materials have been modeled. [•] Effect of EDGs and EWGs was investigated on charge transfer and optical properties. [•] The intra-molecular charge transfer was observed from donor to acceptor moieties. [•] By DFT and TDDFT, different properties were computed. [•] The modeled compounds would be efficient semiconductor materials for multipurpose. [Copyright &y& Elsevier]

Abstract In the present study, the number and position of sulfur atoms on naphthalene diimide (NDI) is systematically investigated to tune its nonlinear optical (NLO) response properties. Our DFT calculations for third-order polarizability (γ) show that the thionation significantly influences the nonlinear optical property of NDI as it is seen among its several designed derivatives (NDI-1 to NDI-10). The smallest and the largest γ zzzz amplitudes are 503.49 × 10−36 and 1299.5 × 10−36 esu for NDI-1 (having tetraone group) and NDI-10 (having tetrathione group), respectively. The increase in γ zzzz amplitude for NDI-10 is 796 × 10−36 esu, which is ∼150% from the γ zzzz amplitude of NDI-1. A comparison of the γ zzzz amplitudes of our designed derivatives are made with para -nitroaniline i.e. a prototype NLO molecule. The γ zzzz amplitude of p NA is found to be 42.64 × 10−36 esu at the same B3LYP/DZVP2 level of theory. Using two-level model, the origin of larger γ zzzz amplitudes is traced in lower transition energy of NDI-10. Furthermore, the calculation of vertical ionization potentials (VIPs) shows that the thionation does not affect the stability of designed derivatives, where a slight difference of 0.06 eV is seen between the VIPs of NDI-1 (6.63 eV) and NDI-10 (6.57 eV). Thus, a systematic comparison of the third-order polarizability and other electro-optical properties of our designed derivatives shows that our derivative systems possess good potential for their practical realization in the field of optical and NLO materials. Graphical abstract Image 1 Highlights • The number and position of sulfur atoms play a crucial role to modulate the NLO response of naphthalene diimide derivatives. • The thionation influences significantly the NLO response of naphthalene diimide derivatives • The naphthalene diimide derivatives possess reasonably larger γ zzzz amplitudes and are good contender for NLO applications. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) response materials are among the smartest materials of the era and are employed to modulate the phase and frequency of the laser. The present study presents a quantum chemical framework for tailoring nitrogen/boron doped derivatives of Dihydrodibenzo [ de , op ]pentacene through terminal and central core modifications. The derivatives of these compounds have been designed by introducing various π-conjugated connectors as well as B/N heteroatoms in the phenalene rings. Density functional theory (DFT) methods are used to optimize the ground state molecular geometries of designed compounds, represented as 1 to 4 (phenalene derivatives) and 1-BN to 4-BN (B/N doped phenalene derivatives) at the M06-2X/6-311G* level of theory. The highest value of 116.9 × 10−24 esu and 240.2 × 10−24 esu for isotropic and anisotropic linear polarizability is shown by compound 4. Among the designed compounds, 4-BN has achieved the highest γ amplitude of 1858 × 10−36 esu owing to its unique molecular structural design. Further analysis of electronic parameters, such as electron density difference (EDD) maps, the density of states, electrostatic potentials, transition density matrix (TDM) analysis, and frontier molecular orbitals analysis (FMOs), demonstrated the more effective intramolecular charge transfer (ICT) for the best compounds, resulting in a good NLO response. The compounds were also analyzed for their potential in photovoltaic applications based on factors such as open circuit voltage values determined to be between (0.14 eV and 1.82 eV), and light harvesting efficiency (0.425–0.909). • A computational framework is proposed by tailoring nitrogen/boron atoms in dihydrodibenzo-pentacene. • The designed compounds showed great variation of optical and NLO properties. • Compound 4-BN has achieved the highest γ amplitude of 1858 × 10−36 esu owing to its tailored push-pull design. • Calculated open circuit voltage observed between 0.14 eV and 1.82 eV, and. • Computed light harvesting efficiency is found from 0.425 to 0.909 for newly designed compounds. [ABSTRACT FROM AUTHOR]

Unlike the previous several investigations on planar donor-π-acceptor chromophores, the present investigation highlights the importance of twisted molecular configurations to effectively tune the optical and nonlinear optical (NLO) response properties. A variety of substitutions are made to design several twisted molecular compounds (1 – 7). These compounds are designed using pyrenyl and naphthalimide moieties, which are twisted with each other in their molecular configurations. The calculated versus experimental highest intensity absorption energy peaks (3.482 V. 3.444 eV) and experimental ionization potentials (6.07 V. 5.93 eV) of parent compound 1 reproduced reasonably well at M06/6-311G∗∗ methodology. The twisted chromophores show significantly larger amplitudes of third-order NLO polarizabilities (<γ>), which are found to be as large as 778.31 × 10−36 esu for compound 7 at the M06/6-311G∗∗ methodology. The <γ> amplitudes were also compared with planar donor-π-acceptor prototype para -nitroaniline (p -NA) molecule to provide the semi-quantitative assessment. For instance, the <γ> amplitudes of all compounds are about ∼7–∼39 times bigger from the amplitude of p -NA at the same computational level. The origin of larger amplitudes has been traced though three-level model using the TD-DFT results. The larger oscillator strengths, lower transitions energies and larger change between the electronic dipole moment between the ground and the excited states. We believe the present study will not only put these compounds under the spotlight of material science but also provide structure-property relationships in designed compounds. Image 1 • The twisted molecular configurations are explored for NLO. • Origin of larger NLO amplitudes traced is in better ICT process. • The hyperpolarizability density (ρ z z z (3) (r)) analysis is performed. • Effects of donor and acceptor substitutions have been studied. • The FMO and MEPs are drawn to see charge distributions. [ABSTRACT FROM AUTHOR]

In the present study, we use the state of art density functional theory (DFT) techniques to calculate the structural, optoelectronic and nonlinear optical (NLO) properties for two novel chalcone derivatives. The geometrical structures of chalcone derivatives compound 1 and 2 are optimized using periodic boundary conditions (PBC) in solid-state phase as well as isolated single molecular geometry in the gas phase. The reasonable agreement is found among experimental, solid-state and gas phase single molecular geometries, which provide us, further confidence to explore the potential of above-entitled derivatives as good functional materials for electro-optical applications. For instance, the frequency dependent real parts of dielectric functions are calculated for compound 1 and 2 . The maximum value of real part of the dielectric function for compound 1 and 2 at 0 eV are computed as 4.35 and 6.68 for the polarization vectors of (001) directions, respectively, which reveals the fact that the compound 1 and 2 might be good charge transport materials. The reflectivities of the compound 1 and 2 are 0.64 and 0.45 revealing that the compound 2 might be more efficient material for organic photovoltaic (OPV) applications. The results of the refractive index improved by doping the strong electron withdrawing groups (EWGs) shows that the compound 2 might be good refractor of the photon as compared to compound 1 . The calculated values for static second-order polarizability are 3498 and 10464 a. u. and for frequency dependent second harmonic generations are 2557 and 6429 a. u. for compound 1 and 2 , respectively, which indicates their significant potential for possible nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Owing to their excellent electrochemical properties, graphenes found applications in several fields ranging from semiconductors, solar cells, field effect transistors, and nanoscale electronic devices as well as in nonlinear optical (NLO) applications. The structural features, electro-optical, charge transport and nonlinear optical properties of the boron-doped graphene (BG) compound 1 were studied using density functional theory methods The BG compound comprises a central electron deficient site of boron atoms, which can serve as electron acceptor while terminal alkoxy groups as donors leading to powerful donor-π-acceptor (D-π-A) configuration. The experimental crystal structure was successfully reproduced by optimized ground state geometry at PBE0/6-311G* level of theory for isolated molecule. The experimental lattice parameters, geometries, crystal presentation and alignment of molecules in the unit cells as well as their packing orientation of BG compound 1 was also efficiently reproduced by applying periodic boundary conditions (PBC) at PBE level. The comprehensive intramolecular charge transfer (CT) was realized from terminal rings of the HOMO to the electron deficient sites of boron atoms of the LUMO. The nature of BG compound 1 might be more towards hole transport even though its hole reorganization energy is twice than that of the electron one due to the significant higher hole transfer integral values. The superior hole transfer integrals and intrinsic mobility values of the BG compound 1 might lead remarkable hole transport contender as compared to many other organic materials. The narrow band gap, density of states profile, dielectric function, uniform conductivity functions and noteworthy electronic as well as CT properties revealed that the BG compound 1 might be proficient optoelectronic contestant having intermolecular CT as well as intramolecular CT with optimal stability. A comparison of static third-order polarizability <γ> of BG compound 1 , as calculated in present investigation, was also performed with some standard NLO molecules as well as graphene nanoflakes. Moreover, longitudinal component γ zzzz of parent compound has been found 12 and 4 times larger than those of previously reported open-shell poly aromatic hydrocarbons (PAH). Interestingly, by increasing the donor ability, i.e., introduction of C 2 H 2 PhNH 2 groups in place of OC 4 H 9 groups (BG compound 3 ) at terminal positions boosts the <γ> amplitude ∼ 8 times than that of its parent BG compound 1 . [ABSTRACT FROM AUTHOR]

The present study explores a series of novel donor-π-acceptor (D-π-A) molecules containing 4,4′-dimethyldiphenylamine moiety as donor, 4,4′-dinitrodiphenylborane as acceptor while different π-bridges as efficient linkers between them, which comprises of (− HC CH −) n , (− Ph −) n and (− Ph ̶ HC CH −) n combinations for compounds in series 1, 2 and 3, respectively. Quantum chemical computations are applied to calculate the linear polarizability (α), first (β) and second (γ) hyperpolarizabilities. A comparative analysis is performed considering an increase of NLO polarizabilities as a function of different π-linkers. Among the investigated compounds, 3c shows the largest first and second hyperpolarizabilities of 1378 × 10−30 and 34971 × 10−36 esu, respectively. Interestingly, an increase in NLO polarizability is observed by modifying the π-conjugated bridges and the largest NLO polarizability is observed for series 3 possessing (Ph ̶ HC CH −) n π-linker which is found due to its lower transition energy and higher oscillator strengths. Furthermore, TD-DFT investigations, frontier molecular orbitals (FMOs) and electron density difference (EDD) maps analysis have shown a more efficient intramolecular charge transfer character from donor to acceptor moieties through (Ph ̶ HC CH −) n π-linkers. The density of states (DOS) maps are showing explicit contributions of electronic states from different fragments of a molecular system where the partial contributions of (Ph ̶ HC CH −) n π-linkers is seen significant in HOMO-LUMO orbitals of all the systems in series number 3. Thus, we believe that our study will highlight the importance of different D-π-A chromophores having variant types of π-conjugation cores as discussed in the present investigation. Schematic and graphical description of the designed D-π-A molecules. Image 1 • Three series of novel D-π-A molecules consisting of (HC=CH) n , (Ph) n and (Ph ̶ HC=CH) n combinations • The NLO polarizabilities are calculated using DFT methods. • All the designed series of compounds show reasonably larger NLO responses. • A structure-NLO property relationship is examined using TD-DFT, FMOs and EDD maps. [ABSTRACT FROM AUTHOR]