Strain-Induced Structural Rearrangement Towards a White-Light-Emitting Adamantane-Type Cluster Dimer.

Group 14/16 adamantane-type hybrid clusters of the type [(RT)4E6] (T=group 14 element, E=group 16 element, R=organic group) have been reported to emit white-light when irradiated in an amorphous state with a continuous-wave (CW) infrared laser diode. This effect is enhanced if the cluster core is varied from a binary to a more complex composition. To further explore this phenomenon, we synthesized clusters with a multinary R/R'-T/T'-E/E' composition, including isolobal replacement of E with CH2, in [(2-NpSi){CH2Sn(S)Ph}3] (1, Np=naphthyl). When expanding one of the CH2 moieties to a C2H4 group, thus generating a R/R'-T/T'-E/E'/E'' cluster composition, we unexpectedly observed a dimerization of the initially formed, yet non-isolable adamantane-like cluster [(2-NpSi){CH2Sn(S)Ph}2{C2H4Sn(S)Ph}] (2) to [(2-NpSi){CH2Sn(S)Ph}2{C2H4Sn(S)Ph}]2 (3), exhibiting a heretofore unprecedented cluster architecture. Both monomeric 1 and dimeric 3, show white-light emission as thin films. The nonlinear optical response of the compounds was also modelled with DFT methods.

Molecular Electrides: An In Silico Perspective.

Electrides are defined as the ionic compounds where the electron(s) serves as an anion. These electron(s) is (are) not bound to any atoms, bonds, or molecules but are rather localized into the space, crystal voids, or interlayer between two molecular slabs. There are three major categories of electrides, known as organic electrides, inorganic electrides, and molecular electrides. The computational techniques have proven as a great tool to provide emphasis on the electride materials. In this review, we have focused on the computational methodologies and criteria that help to characterize molecular electrides. A detailed account of the computational methods and basis sets applicable for molecular electrides have been discussed along with their limitations in this field. The main criterion for the identification of the electrides has also been discussed thoroughly with proper examples. The molecular electrides presented here have been justified with all the required criteria that support and proved their electride characteristics. We have also presented few systems which have similar properties but are not considered as molecular electrides. Moreover, the applicability of the electrides in catalytic processes have also been presented.

N-Arylation of Protected and Unprotected 5-Bromo-2-aminobenzimidazole as Organic Material: Non-Linear Optical (NLO) Properties and Structural Feature Determination through Computational Approach.

The interest in the NLO response of organic compounds is growing rapidly, due to the ease of synthesis, availability, and low loss. Here, in this study, Cu(II)-catalyzed selective N-arylation of 2-aminobenzimidazoles derivatives were achieved in the presence of different bases Et3N/TMEDA, solvents DCM/MeOH/H2O, and various aryl boronic acids under open atmospheric conditions. Two different copper-catalyzed pathways were selected for N-arylation in the presence of active nucleophilic sites, providing a unique tool for the preparation of NLO materials, C-NH (aryl) derivatives of 2-aminobenzimidazoles with protection and without protection of NH2 group. In addition to NMR analysis, all synthesized derivatives (1a-1f and 2a-2f) of 5-bromo-2-aminobenzimidazole (1) were computed for their non-linear optical (NLO) properties and reactivity descriptor parameters. Frontier molecular orbital (FMO) analysis was performed to get information about the electronic properties and reactivity of synthesized compounds.

Impact of Ion-Pairing Effects on Linear and Nonlinear Photophysical Properties of Polymethine Dyes*.

The two-photon absorption (2PA) and photophysics of heptamethine dyes featuring cyanine or dipolar electronic structures have been compared for the first time. The perfectly delocalized cyanine system is classically characterized by a two-photon transition matching the vibronic component of its lower energy absorption band. The dipolar species is generated by ion-pairing with a hard counterion in a non-dissociating solvent and displays significant modifications oft he optical properties, including a significant hypochromic shift of absorption, weaker emission and 2PA matching the lower energy transition, thus revealing symmetry breaking within the polymethine electronic structure.

Selective Arylation of 2-Bromo-4-chlorophenyl-2-bromobutanoate via a Pd-Catalyzed Suzuki Cross-Coupling Reaction and Its Electronic and Non-Linear Optical (NLO) Properties via DFT Studies.

In the present study, 2-bromo-4-chlorophenyl-2-bromobutanoate (3) was synthesized via the reaction of 2-bromo-4-chlorophenol with 2-bromobutanoyl bromide in the presence of pyridine. A variety of 2-bromo-4-chlorophenyl-2-bromobutanoate derivatives (5a-f) were synthesized with moderate to good yields via a Pd-catalyzed Suzuki cross-coupling reaction. To find out the reactivity and electronic properties of the compounds, Frontier molecular orbital analysis, non-linear optical properties, and molecular electrostatic potential studies were performed.

Excited State and Non-linear Optical Properties of NIR Absorbing ß-Thiophene-Fused BF2-Azadipyrromethene Dyes-Computational Investigation.

Density functional theory and time-dependent density functional theory computations were used to understand the electronic and photophysical parameters of NIR ß-thiophene-fused BF2-azadipyrromethene dyes. The computed data are in good agreement with those obtained experimentally and they provide insights into the origin of red shifted optical spectra compared to the parent aza-BODIPY, low Stokes shift, non-linear optical responses and quantitative description of the singlet-triplet energy gap. The resultant decrease in the HOMO - LUMO energy gap is responsible for the red shift. The possible use as non-linear optical materials is supported by large enhancement in the non-linear optical properties. On the basis of vertical triplet energies, their possible potential therapeutic use as a photosensitizer in photodynamic therapy is proposed. The singlet-triplet energetic gaps suggest that the ß-thiophene-fused BF2-azadipyrromethene dyes can act as a sensitizer to produce an efficient generation of singlet oxygen. Their optimal use as an efficient singlet fission materials has been proposed on the basis of excitation energies in the ground, lowest singlet and triplet excited states.

Enhancement in Two-Photon Absorption and Photoluminescence in Single Crystals of Cd(II) Metal Organic Frameworks.

The emergence of metal organic frameworks (MOFs) as advanced photonic materials has placed them at the forefront of exploration. Nonlinear optical (NLO) phenomena such as simultaneous two-photon absorption and consequent upconversion emission have been in demand for promising applications. A rational design approach based on the fundamental structure-property relationship is key for the fabrication of nonlinear optically active MOF materials. Here, we investigate two-photon-absorption (2PA)-induced photoluminescence of four new Cd(II) MOFs based on an acceptor-π-donor-π-acceptor trans, trans-9, 10-bis(4-pyridylethenyl)anthracene chromophore linker. The use of auxiliary carboxylate linkers resulted in the variation of crystal structures, leading to the modulation of NLO properties. On comparison with a standard Zn(II)-MOF, two MOFs showed enhancement in 2PA, while the other two showed a mild decrease. We tried to establish a structural correlation to explain the trend in NLO activity. The interplay of various factors such as chromophore density, degree of interpenetration, chromophore orientation, and π···π interactions between the individual networks affects the NLO activities. These results show the modulation of the optical properties of MOFs based on a combined strategy for the development of tunable single crystal NLO devices.

An investigation into the structural, electronic, and non-linear optical properties in CN (N = 20, 24, 26, 28, 30, 32, 34, 36, and 38) fullerene cages.

The present study attempts to investigate the structural, electronic, and non-linear optical properties of CN (N = 20, 24, 26, 28, 30, 32, 34, 36, and 38) fullerene cages based on Density Functional Theory (DFT). In the DFT calculations, the B3LYP/6-311G(d,p) and CAM-B3LYP/6-311 + + G(d,p) level of theories were used. The isomers of each fullerene have been received from the Fullerene Structure Library. These isomers have optimized using the B3LYP/6-311G(d,p). The results included optimization of the neutral and ionic state structures according to their multiplicity. Geometries, optimization energies, relative energies, frequencies, HOMO, LUMO, and HOMO-LUMO gap of these stable fullerene cages have been predicted by B3LYP/6-311G(d,p). Afterwards, the most stable structures have been re-optimized using the CAM-B3LYP /6-311 + + G(d,p). Finally, non-linear optical properties, Fukui functions, density of state, electron affinity, and ionization potential values of the most stable fullerene cages have been found out by the DFT/ CAM-B3LYP /6-311 + + G(d,p) level of theory. All calculation results have been compared with both C60 fullerene and the relevant literature on corresponding fullerenes.

Whole-mol-ecule disorder of the Schiff base compound 4-chloro-N-(4-nitro-benzyl-idene)aniline: crystal structure and Hirshfeld surface analysis.

In the crystal of the title Schiff base compound, C13H9ClN2O2, [CNBA; systematic name: (E)-N-(4-chloro-phen-yl)-1-(4-nitro-phen-yl)methanimine], the CNBA mol-ecule shows whole-mol-ecule disorder (occupancy ratio 0.65:0.35), with the disorder components related by a twofold rotation about the shorter axis of the mol-ecule. The aromatic rings are inclined to each other by 39.3 (5)° in the major component and by 35.7 (9)° in the minor component. In the crystal, C-H⋯O hydrogen bonds predominate in linking the major components, while weak C-H⋯Cl inter-actions predominate in linking the minor components. The result is the formation of corrugated layers lying parallel to the ac plane. The crystal packing was analysed using Hirshfeld surface analysis and compared with related structures.

Quantum computational study of non-linear optical properties of some phenanthrene derivatives.

Non-linear optical (NLO) behavior of some phenanthrene-based organic molecules is studied using quantum computational MP2 and B3LYP methods with cc-pVDZ basis set. The design of these molecules is based on possible intramolecular charge transfer between electron donor and electron acceptor groups via an aromatic bridge. The -NO2, -CN, -CF3, -C(CF3)C(CF3)2, -SO3H and -C(CN)C(CN)2 acceptors and the -NH2, -N(CH3)2 and pyrrolidinyl donors have been considered. The HOMO and LUMO energies, polarizabilities and first hyperpolarizabilities are calculated for the optimized structures both in the gas phase and in the conductor-like polarizable continuum model (CPCM) of different solvents. Moreover, the energies of the vertical transitions in the UV-Vis range having large oscillator strengths and their corresponding adiabatic transition energies are calculated using TD-DFT-B3LYP/cc-pVDZ method. Also, UV-Vis and infrared spectra are simulated for these designed molecules. Results show that these phenanthrene derivatives have generally very good NLO behavior. Also, NLO properties are enhanced when (-C(CN)C(CN)2 & -NH2) and (-NO2 & pyrrolidinyl) pairs of (acceptor & donor) groups are used. The approach adopted in the present quantum computational study can be used for similar studies for better description and understanding of the NLO responses of the electron donor-bridge-acceptor systems with π-conjugated bridges.

Gold Nanorods as Saturable Absorber for Harmonic Soliton Molecules Generation.

Gold nanorods (GNRs) has been investigated in the field of chemistry, optoelectronics, and medicine for their tenability, compatibility, electromagnetics, and excellent photonics properties. Especially, GNRs, used to generate ultrashort pulse, have been studied recently. However, multiple pulses evolution based on GNRs needs to be further explored. In this article, GNRs are synthesized by seed-mediated growth method, characterized systematically and been chosen as saturable absorber (SA) to apply in ultrafast photonics. The GNRs SA presents a saturable intensity of 266 MW/cm2, modulation depth of 0.6%, and non-saturable loss of 51%. Furthermore, a passively mode-locked erbium-doped fiber laser based on GNRs SA with femtosecond pulse is demonstrated. Thanks to the excellent properties of GNRs, by adjusting the cavity polarization direction with the proposed GNRs SA, soliton molecules operation with spectrum modulation period of 3.3 nm and pulse modulation interval of 2.238 ps is directly obtained. For the most important, 9th-order harmonic soliton molecules have been generated in the laser cavity for the first time. It is demonstrated that GNRs can be a novel type of non-linear optical (NLO) device and have potential applications in the field of ultrafast photonics.

Synthesis, structure and non-linear optical properties of new isostructural ß-D-fructopyranose alkaline halide metal-organic frameworks: a theoretical and an experimental study.

In this work four metal-organic framework isomorphs, based on fructose and alkali-earth halogenides, were investigated to better understand the effect of the size of the cation and the different polarizability of the anion on the calculated hyperpolarizability and optical susceptibility, which are correlated to non-linear optical properties. The compounds were characterized by X-ray diffraction and the first hyperpolarizability and the second-order susceptibility were obtained from theoretical calculations. Furthermore, a new method to measure the second-harmonic (SH) efficiency on a small quantity of powder at different wavelengths of excitation was optimized and an attempt was made to assess the reduction of the SH intensity for small quantities of nano-crystals, in order to ascertain the possibility of applications in biological systems. The results of this work show that both the intrinsic nature of the anion and the induced dissociation of cations and anions by fructose play a role in the second-harmonic generating properties of such compounds.

Crystal structure of 2-ethyl-4-methyl-1-(2-oxido-3,4-dioxo-cyclo-but-1-en-1-yl)-1H-imidazol-3-ium.

In the title inner salt molecule, C10H10N2O3, the four-membered cyclobutene ring is twisted by 7.1 (2)° with respect to the five-membered imidazole ring. The crystal packing exhibits an R 2 (2)(9) hydrogen-bonding ring motif through N-H⋯O and C-H⋯O inter-actions. The potential non-linear optical properties were studied by a computational ab initio calculations performed at the DFT/B3LYP/6-31++G(d,p) level of theory.

Enhancement of nonlinear optical (NLO) properties of indigo through modification of auxiliary donor, donor and acceptor.

In this study, indigo based dyes with high non-linear optical response have been investigated. Density functional theory (DFT) was used to study non-linear optical properties of indigo and newly designed dyes (IM-Dye-0, IM-Dye-1, IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. The HOMO-LUMO energy gaps of newly designed dyes were smaller as compare with indigo dye. Absorption maxima of newly designed dyes strongly red shifted as compare with indigo dye. High non-linear optical (NLO) response of newly designed dyes revealed that these materials would be excellent for NLO applications. This theoretical approach of designing will pave the way for experimentalists to synthesize high response NLO compound.

Crystal structure, spectroscopic studies and quantum mechanical calculations of 2-[((3-iodo-4-methyl)phenylimino)methyl]-5-nitrothiophene.

The title compound, 2-[((3-iodo-4-methyl)phenylimino)methyl]-5-nitrothiophene, C12H9O2N2I1S1, was synthesized and characterized by IR, UV-Vis and single-crystal X-ray diffraction technique. The molecular structure was optimized at the B3LYP, B3PW91 and PBEPBE levels of the density functional method (DFT) with the 6-311G+(d,p) basis set. Using the TD-DFT method, the electronic absorption spectra of the title compound was computed in both the gas phase and ethanol solvent. The harmonic vibrational frequencies of the title compound were calculated using the same methods with the 6-311G+(d,p) basis set. The calculated results were compared with the experimental determination results of the compound. The energetic behavior such as the total energy, atomic charges, dipole moment of the title compound in solvent media were examined using the B3LYP, B3PW91 and PBEPBE methods with the 6-311G+(d,p) basis set by applying the Onsager and the polarizable continuum model (PCM). The molecular orbitals (FMOs) analysis, the molecular electrostatic potential map (MEP) and the nonlinear optical properties (NLO) for the title compound were obtained with the same levels of theory. And then thermodynamic properties for the title compound were obtained using the same methods with the 6-311G(d,p) basis set.

Synthesis, characterization of (3E)-1-(6-chloro-2-methyl-4-phenyl quinolin-3-Yl)-3-aryl prop-2-en-1-ones through IR, NMR, single crystal X-ray diffraction and insights into their electronic structure using DFT calculations.

3E-1-(6-Chloro-2-methyl-4-phenylquinolin-3-yl)-3-arylprop-2-en-1-ones were synthesized and characterized by FTIR, (1)H NMR, (13)C NMR, HSQC, DEPT-135. In addition the compound 3E-1-(6-chloro-2-methyl-4-phenylquinolin-3-yl)-3-(2,5-dimethoxyphenyl)prop-2-en-1-one was subjected to the single crystal X-ray diffraction studies. Density functional theory calculations were carried out for this chalcone and its derivatives to investigate into their electronic structure, chemical reactivity, linear and non-linear optical properties. The structure predicted from DFT for chalcone is in good agreement with the structure from XRD measurement.

Computational studies of the electronic, conductivities, and spectroscopic properties of hydrolysed Ru(II) anticancer complexes.

The mechanism of activation of metal-based anticancer agents was reported to be through hydrolysis. In this study, computational method was used to gain insight to the correlation between the chemistry of the hydrolysis and the anticancer activities of selected Ru(II)-based complexes. Interestingly, we observed that the mechanism of activation by hydrolysis and their consequential anticancer activities is associated with favourable thermodynamic changes, higher hyperpolarizability (ß), lower band-gap and higher first-order net current. The Fermi contact (FC) and spin dipole (SD) are found to be the two most significant Ramsey terms that determine the spin-spin couplings (J(HZ)) of most of the existing bonds in the complexes. Many of the computed properties give insights into the change in the chemistry of the complexes due to hydrolysis. Besides strong correlations of the computed properties to the anticancer activities of the complexes, using the quantum theory of atoms in a molecule (QTAIM) to analyse the spectroscopic properties shows a stronger correlation between the spectroscopic properties of Ru atom to the reported anticancer activities than the sum over of the spectroscopic properties of all atoms in the complexes.

Synthesis, spectroscopic (FT-IR/NMR) characterization, X-ray structure and DFT studies on (E)-2-(1-phenylethylidene) hydrazinecarboximidamide nitrate hemimethanol.

The title molecular salt, (E)-2-(1-phenylethylidene) hydrazinecarboximidamide nitrate hemimethanol C9H13N4(+)·NO3(-)·0.5CH4O, was synthesized and characterized by elemental analysis, FT-IR and NMT spectroscopies, and single-crystal X-ray diffraction technique. Quantum chemical calculations were performed to study the molecular and spectroscopic properties of the title compound, and the results were compared with the experimental findings. The calculated results show that the optimized geometry can well reproduce the crystal structure parameters, and the theoretical vibrational frequencies and GIAO (1)H and (13)CNMR chemical shifts show good agreement with experimental values. The dipole moment, linear polarizability and first hyperpolarizability values were also computed. The linear polarizabilities and first hyper polarizabilities of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H) and temperatures.