Aijaz Rasool Chaudhry

How does hybrid bridging core modification enhance the nonlinear optical properties in donor-π-acceptor configuration? A case study of dinitrophenol derivatives

This study spotlights the fundamental insights about the structure and static first hyperpolarizability (β) of a series of 2,4‐dinitrophenol derivatives (1–5), which are designed by novel bridging core modifications. The central bridging core modifications show noteworthy effects to modulate the optical and nonlinear optical properties in these derivatives. The derivative systems show significantly large amplitudes of first hyperpolarizability as compared to parent system 1, which are 4, 46, 66, and 90% larger for systems 2, 3, 4, and 5, respectively, at Moller–Plesset (MP2)/6‐31G* level of theory. The static first hyperpolarizability and frequency dependent coupled‐perturbed Kohn–Sham first hyperpolarizability are calculated by means of MP2 and density functional theory methods and compared with respective experimental values wherever possible. Using two‐level model with full‐set of parameters dependence of transition energy (ΔΕ), transition dipole moment (μ0) as well as change in dipole moment from ground to excited state (Δμ), the origin of increase in β amplitudes is traced from the change in dipole moment from ground to excited state. The causes of change in dipole moments are further discovered through sum of Mulliken atomic charges and intermolecular charge transfer spotted in frontier molecular orbitals analysis. Additionally, analysis of conformational isomers and UV‐Visible spectra has been also performed for all designed derivatives. Thus, our present investigation provides novel and explanatory insights on the chemical nature and origin of intrinsic nonlinear optical (NLO) properties of 2,4‐dinitrophenol derivatives.

Tuning the push–pull configuration for efficient second-order nonlinear optical properties in some chalcone derivatives

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 (μtot), polarizability (α0) and static first hyperpolarizability (βtot) amplitudes for parent system 1 are found to be 5.139 Debye, 274a. u. and 24.22×10(-30)esu, respectively. These amplitudes have been significantly enhanced in designed derivatives 2 and 3. More importantly, the (βtot) 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 μβω (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 1400nm 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 544nm. Thus, the present work realizes the potential of designed derivatives as efficient NLO-phores for modern NLO applications.

The effect of anchoring groups on the electro-optical and charge injection in triphenylamine derivatives@Ti6O12

The triphenylamine (TPA), thiophene and pyrimidine are being used as efficient advanced functional semiconductor materials. In the present study, some new TPA donor–π–acceptor derivatives were designed where TPA moiety acts as donor, thiophene-pyrimidine π-bridge and acetic/cyanoacetic acid as acceptor. The ground-state geometries were optimized at B3LYP/6-31G** level of theory. The excitation energies and oscillator strengths were computed at TD-CAM-B3LYP/6-31G** (polarizable continuum model (PCM), in methanol) level of theory. The electronic, photophysical and charge transport properties were calculated wherever possible the computed values were compared with the available experimental as well as computational data. The electron injection (ΔGinject), relative electron injection , electron coupling constants (∣VRP∣) and light harvesting efficiencies (LHE) have been calculated and compared with referenced compounds. The energies of the lowest unoccupied molecular orbitals (ELUMOs), diagonal bandgaps and energy level offsets were studied to shed light on the electron transport behavior. The effect of anchoring groups (acetic acid and cyanoacetic acid) was studied on the properties of interests in the dye and dye@Ti6O12. It was observed that after interaction of dye with the TiO2 cluster intra-molecular charge transport enhanced from HOMO of the dye to LUMO of the semiconductor cluster. The cyanoacetic acid anchoring group leads the superior LHE, ΔGinject and ∣VRP∣ which might improve the solar cell performance.

Role of a singlet diradical character in carbon nanomaterials: a novel hot spot for efficient nonlinear optical materials

Carbon atoms have the potential to produce a variety of fascinating all-carbon structures with amazing electronic and mechanical properties. Over the last few decades, several efforts have been made using experimental and computational techniques to functionalize graphene, carbon nanotubes and fullerenes for potential use in modern hi-tech electronic, medicinal, optical and nonlinear optical (NLO) applications. Since photons replaced electrons as a carrier of information, the field of NLO material design has drawn immense interest in contemporary materials science. There have been several reports of bridging the gap between the exciting fields of carbon nanomaterials and NLO materials by functionalizing carbon nanomaterials for potential NLO applications. In contrast to previous reports of the design of third-order NLO materials using conventional closed-shell materials, a novel strategy using open-shell diradical molecular systems has recently been proposed. Quantum chemically, diradical character is explained in terms of the instability of the chemical bonds in open-shell molecular systems. Interestingly, several carbon nanomaterials, which naturally possess open-shell singlet configurations, have recently gained momentum in the design of these classes of open-shell NLO materials with excellent NLO properties, stability and diversity. The present review establishes a systematic sequence of different studies (spanning over two decades of intense research efforts), starting from the simplest theoretical two-site diradical model, continuing to its experimental and theoretical realization in actual chemical systems, and finally applying the abovementioned model/rule to novel carbon nanomaterials to tune their NLO properties, particularly their second hyperpolarizability (γ). In the present report, we highlight several recent efforts to functionalize carbon nanomaterials by exploiting their open-shell diradical character to achieve efficient third-order NLO properties. Several issues and opportunities are discussed, including the inherited disadvantages of both experimental (the high reactivity and short life of diradical compounds) and quantum (need for multi-reference methodology) techniques when dealing with carbon nanomaterials. A comparative analysis of several quantum chemical investigations, along with contemporary experimental results, will be performed to emphasize the core issues and opportunities related to carbon nanomaterials with singlet open-shell diradical character. Thus, the present review will highlight carbon nanomaterials with diradical/biradical character for their prospective applications in the NLO field.

Influence of push-pull configuration on the electro-optical and charge transport properties of novel naphtho-difuran derivatives: A DFT study

We present a density functional theory (DFT) study pertaining to electro-optical and charge transport properties of two novel derivatives of diphenyl-naphtho[2,1-b:6,5-b′]difuran (DPNDF) as investigated based on push-pull configuration. Both molecular structures of the designed derivatives were optimized, in ground state (S0) as well as excited state (S1), using DFT and time-dependent DFT (TD-DFT) respectively. The push-pull configuration effect was studied meticulously for different electro-optical properties including adiabatic/vertical electron affinity (EAa/EAv), adiabatic/vertical ionization potential (IPa/IPv) and hole/electron reorganization energies (λh/λe), hole/electron transfer integrals (Vh/Ve), hole/electron mobility and photostability. We observed smaller λe, improved Ve and higher electron mobility for compound 1 compared with the parent molecule. Our calculated value of the electron mobility for compound 1 (2.43 cm2 V−1 s−1) revealed it to be an efficient electron transport material. Moreover, the influence of the push-pull on the electronic structure was also investigated by calculating the total and partial density of states (DOS). Taking advantage of the strong push-pull configurations effect on other properties, the study of the designed chemical systems was extended to their nonlinear optical (NLO) properties. Our designed novel derivatives (1 & 2) exhibited significantly larger amplitude values for first hyperpolarizability with βtot equal to 209.420 × 10−30 esu for compound 1 and 333.830 × 10−30 esu for compound 2. It was found that the first hyperpolarizability and HOMO–LUMO energy gap are in an inverse relationship for compounds 1 and 2.

First principles study for the key electronic, optical and nonlinear optical properties of novel donor-acceptor chalcones

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 , 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 for comp.1 and comp.2 are found to be 32.15×10-24 and 38.76×10-24esu, respectively. Similarly, the second hyperpolarizability amplitudes of comp.1 and comp.2 are found to be reasonably larger mounting to 79.31×10-36 and 181.36×10-36esu, 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 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 shows that 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.

Exploring the potential of boron-doped nanographene as efficient charge transport and nonlinear optical material: A first-principles study

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 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 γzzzz 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 C2H2PhNH2 groups in place of OC4H9 groups (BG compound 3) at terminal positions boosts the amplitude∼8 times than that of its parent BG compound 1.

Quantum chemical investigation of spectroscopic studies and hydrogen bonding interactions between water and methoxybenzeylidene-based humidity sensor

A quantum chemical investigation has been performed to spotlight the structure–property relationship among methoxybenzeylidene-based humidity sensor and water molecules. The chemical interactions among (E)-2-(4-(2-(3,4-dimethoxybenzeylidene)hydrazinyl)phenyl) ethane-1,1,2-tricarbonitrile (DMBHPET) sensor and water molecules have been studied using density functional theory (DFT) methods. The molecular structural parameters, binding energies and Infrared (IR) spectroscopic analyses have been performed to assess the nature of intermolecular interactions. Three different positions have been identified for possible attachments of H2O molecules through hydrogen bonding interactions. These positions include NH (complex 1a), p-OCH3 (complex 1b) and N=N (complex 1c) group in sensor molecule (1) for the chemical adsorption of water molecules. While, the complex 1abc includes all three sites with simultaneously three H2O molecules attached to it through hydrogen bonding. The binding energies calculated for complex 1a(NH…H2O), complex 1b(CH3O…H2O), complex 1c(N=N…H2O) and complex 1abc are -30.97, -18.41, -13.80 and -65.36 kcal/mol, respectively. The counterpoise (CP) scheme has been used to correct the basis set superposition error (BSSE) in calculation of binding energies of sensor and H2O complexes. The higher binding energy of -65.36 kcal/mol for complex 1abc represents that the present methoxybenzeylidene-based sensor has significant potential through hydrogen bonding formation for sensing humidity as indicated in our previous experimental investigation. The evidence of hydrogen bonding interactions between sensor 1 and H2O molecules has been traced through structural parameters, red shift in IR spectra as well as molecular electrostatic maps. Thus the present investigation highlights the first computational framework for a molecular level structure-binding activity of a methoxybenzeylidene-based sensor and water molecules.

How does the increment of hetero-cyclic conjugated moieties affect electro-optical and charge transport properties of novel naphtha-difuran derivatives? A computational approach

AbstractWe have investigated computationally the effects of π-conjugation extension on naphtha[2,1-b:6,5-b’] difuran (DPNDF); where we increase the number of fused NDF (central core) and furan rings in the parent molecule. The molecular structures of all analogues have been optimized at the ground (S0) and first excited (S1) states using density functional theory (DFT) and time-dependent density functional theory (TD-DFT), respectively. Then highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs), photophysical properties, adiabatic/vertical electron affinities (EAa)/(EAv), adiabatic/vertical ionization potentials (IPa)/(IPv), and hole/electron reorganization energies λh/λe have been investigated. The effect of NDF and furan rings on structural and electro-optical properties has also been studied. Our calculated reorganization energies of 1a, 1b, and 2c reveal them, materials with balanced hole/electron charge transport, whereas 2a and 2b are good hole-transport materials. By increasing the number of furan rings; the photostability was augmented in 2a, 2b, and 2c. Graphical AbstractComputed emission spectra, at the TD-B3LYP/6-31G** level of theory

Exploring the possible existence of oxygen-bridged planarized 4-aminopyridine: promising structure, charge transport and nonlinear optical properties

In the present quantum chemical investigation, for the first time, we shed light on the promising structure, charge transport and nonlinear optical properties (NLO) of oxygen-bridged planarized 4-aminopyridine (APY3O3). Density functional theory (DFT) and time dependent DFT methods are used to elucidate the novel structure, optical and NLO properties of open 4-aminopyridine (APY3) as well as oxygen-bridged closed APY3O3 systems. The calculated third-order polarizability 〈γ〉 for APY3 and APY3O3 is found to be 76.85 and 89.16 × 10−36 esu with the B3LYP method and the 6-311G** basis set, respectively, which is ∼10 and 12 times larger than that of para-nitroaniline (a prototype NLO molecule). Calculation of the electron affinity and reorganization energy suggests that good electron transfer properties are feasible by changing the geometry from open APY3 to closed APY3O3 through oxygen bridging. Interestingly, the configuration of a dimer having APY3O3 and oxygen-bridged triphenylborane (TPBO3) monomers demonstrates remarkable enhancement in NLO response through a novel non-covalent intermolecular charge transfer process. The present investigation not only evokes scientific interest regarding the promising structure of APY3O3 but also highlights its several optical and NLO properties that can be beneficial for its use as an advanced functional material in modern hi-tech applications.