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Carboxylic acid supramolecular synthon exhibited dimer or catemer motifs in the crystal lattice depend on the substituent and other functional groups present in the structure. In general, presence of other competing functional groups produced catemer motifs, whereas unsubstituted acids showed dimer. In this manuscript, we have synthesized a new aryl ether amine-based Schiff base with carboxylic acid functionality (1) and demonstrated polymorphic structure via catemer (1a) and dimer (1 b) motifs in the solid state. In both the structure, carboxylic acid group adopted different orientation in the crystal lattice. The different H-bonding lead to modulation of optical properties that was further supported highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) calculation. Further the stability calculation indicates that dimer (1 b) structure was more stable by 8.54 kcal/mole relative to catemer (1a) motifs. Further, the supramolecular interactions in catemer (1a) and dimer (1 b) motifs was studied by Hirshfeld surface and fingerprint plots to gain insight and compare the different functional groups contribution for intermolecular interactions in the polymorphic crystals which clearly showed different intermolecular interactions in polymorphs. [ABSTRACT FROM AUTHOR]

We designed six 4,6-di(pentacenothiophene-2-yl)pyrimidine molecules with excellent charge transport properties. The optimization of ground-state geometries with B3LYP/6-31G** level is adopted with the help of first-principle investigations. The bridge elongation strategy was employed to strengthen intra-molecular charge transfer. The time-dependent density functional theory (TDDFT) was employed for the measurement of absorption spectra (λabs). The λabs, energy gaps (Egaps), frontier molecular orbitals (FMOs) energies, electron injection, ionization energy (IE), electron affinity (EA) along with reorganization energy (λ) values were computed. The substitution of long-chain polyacene cores as well as thiophene enhanced the EA, reduces hole/electron λ along with their IE. The λ(h), and λ(e), were compared with hole and electron transfer within mostly used compounds, like pentacene and tris(8-hydroxyquinolinato)aluminum (mer-Alq3), respectively. It is anticipated that novel designed compounds may be better to be used for hole transfer (as pentacene) and electron transfer (as mer-Alq3) compounds. These derivatives would act as productive materials that can be employed as p- and n-type semiconductors. The elongation of oligothiophene and acene cores act as excellent hole transfer materials that may be better than frequently used p-type reference compounds. These designed derivative also showed lower λ (e) values exhibited that these may be best/comparable with commonly used n-type mer-Alq3. [ABSTRACT FROM AUTHOR]

Charge transport and electronic character of fluorophore chalcogenides 4,4-Difluoro-8-(-XC4H3)-4-bora-3a,4a-diaza-s-indacene (X = O, S, Se) (BODIPY) derivatives were examined at the molecular level. The effect of chalcogenides was investigated on the transfer integrals, electron affinity (EA), frontier molecular orbitals (FMO), ionisation energy (IE), intrinsic mobility along with reorganisation energies. The ring dissimilarities within 4,4-difluoro-8-(-XC4H3)-4-bora-3a,4a-diaza-s-indacene (X = O, 2-/3-furyl (Comp1/Comp4)); (X = S, 2-/3-thienyl (Comp2/Comp4)) and (X = Se, 2-/3-selenenyl (Comp3/Comp6)) were compared systematically. Among BODIPY chalcogenides derivatives, 2-furyl substitution is more beneficial compared with 2-thienyl, 2-selenenyl and 3-furyl as the prior moiety significantly increases intrinsic hole mobility. The –S or –Se substitution at 2- or 3- position in place of –O at equivalent position reduces the structural polarisation from neutral to cation resulting in reduced hole reorganisation energies. The doping of –S or –Se at 2-position decreases the hole transfer integral in comparison to 2-furyl-substituted derivative. The effect of chalcogen atoms on 2- or 3- position is not so significant on the HOMO/LUMO energy levels. It is expected that –O doping at 2-position in furyl is supporting p-type charge transport channel. These results demonstrated that the studied BODIPY derivatives would be efficient hole transfer materials to be used in organic semiconductor devices. [ABSTRACT FROM AUTHOR]

Three novel pyrimidine based bis-uracil derivatives 1–3 were synthesized by the condensation reaction of 2-hydroxynaphthaldehyde with 6-amino-1,3-dimethylpyrimidine-2,-4(1H, 3H)-dione; 6-amino-1, 3-diethylpyrimidine-2,-4(1H, 3H)-dione, and 6-amino-1,-ethyl-3-methylpyrimidine-2,-4(1H, 3H)-dione, respectively and structurally characterized. The preliminary test of compounds was evaluated by SwissADME that can predict rapidly key parameters for a collection of molecules to support their drug discovery endeavors. Antimicrobial, photoluminescence, and molecular docking of compounds were also studied. The kinetic and thermal stabilities along with intramolecular charge transfer characters were obtained for compounds using frontier molecular orbitals, electrostatic potential diagrams as well as their orbital energies. Additionally, we applied state-of-art computational methods to assess the linear and nonlinear optical (NLO) properties of compounds at M06/6-311G** levels of theory. The third-order NLO properties of 1–3 were observed larger as compared to the standard indicating the considerable NLO character of all molecules, which may render the above derivatives as efficient candidates for NLO device fabrications. [ABSTRACT FROM AUTHOR]

In the present study, we report synthesis, characterization, structural and theoretical studies of two copper(II) complexes, [Cu(py)2(L1)2] (1) and [Cu(phen)(Ac)2-Cu2(Ac)4]n (2), and a nickel(II) complex, [Ni(bipy)(L)(Ac)] (3), where py = pyridine, L1 = 3,5-dichloro-2-hydroxybenzaldehyde, phen = 1,10-phenanthroline, Ac = acetate ion, bipy = 2,2'-bipyridine and HL = 4-bromo-2-(Z)-(naphthalene-2-ylimino)methyl) phenol. The new complexes were fully characterized using microanalysis, FAB-mas (m/z), FT-IR, UV-Vis and fluorescence spectra, X-band EPR spectroscopy and then by single crystal X-ray diffraction studies. X-ray studies of 1 and 3 revealed distorted octahedral geometries. Complex 2 is a coordination polymer built by an octahedral copper unit Cu(phen)(Ac)2 alternating with paddle wheel species Cu2(Ac)4, located on a crystallographic center of symmetry, where an acetate anion bridges the two crystallographic independent copper ions. The fluorescence intensities and quantum yields of 1 and 2 were found to be more compared to 3. The preliminary tests in the potential application for theoretical biological activities of compounds have also been studied. Furthermore, we also performed quantum chemical calculations to get insights into the structure-property relationships of the synthesized complexes. The quantum chemical calculations were used for theoretical calculations of linear polarizability and third-order nonlinear optical polarizability (γ) for 1, 2 and 3. Besides this, the theoretical calculations, including the analysis of frontier molecular orbitals and electrostatic potential diagrams, are used to highlight the theoretical aspects of metal to ligand charge transfer (MLCT) processes in the studied complexes. [ABSTRACT FROM AUTHOR]