Tailoring the band-gap, optical and fluorescent properties of 3,5-diaminobenzoic acid via functionalization with chemical groups: A DFT study.

3,5-diaminobenzoic acid (3,5-DABA) with chemical formula C7H8N2O2 was functionalized with CH3-, OH-, NH2- and NO2- to obtain: CH3-3,5 DABA, OH-3,5 DABA, NH2-3,5DABA and NO2-3,5DABA. These molecules were built with Gauss view 6.0 and their structural, spectroscopic, optoelectronic and molecular properties were investigated using density functional theory (DFT). B3LYP (Becke's 3-parameter exchange functional with Lee-Yang-Parr correlation energy) functional and 6-311+ G (d, p) basis set were used to understand their reactivity, stability and optical activity. Integral equation formalism polarizable continuum model (IEF - PCM) was used to calculate the absorption wavelength, energy required to excite the molecules and oscillator strength. Our results reveal that the functionalization of 3,5 DABA with the groups caused a decrease of the energy gap from 0.1563 eV, to 0.1461 eV, 0.13818 eV and 0.13811 eV in NO2-3,5DABA, OH-3,5DABA and NH2-3,5DABA respectively. The lowest energy gap of 0.13811 eV for NH2-3,5DABA is in good agreement with its highest reactivity value (global softness of 7.240). The most observed significant donor - acceptor NBO interactions where found to occur between *ΠC16-O17 → *ΠC1-C2, *ΠC3-C4→ *ΠC1-C2, *ΠC1-C2 → *ΠC5-C6, *ΠC3-C4 → *ΠC5-C6, *ΠC2-C3 →*ΠC4-C5 natural bond orbitals having second- order stabilization energies of 101.95 kcal/mol, 368.41 kcal/mol, 174.51 kcal/mol, 255.63 kcal/mol and 235.92 kcal/mol in 3,5-DABA, CH3-3,5-DABA, OH-3,5-DABA, NH2-3,5-DABA and NO2-3,5-DABA respectively. The highest perturbation energy was observed in CH3-3,5DABA while the lowest perturbation energy was observed in 3,5DABA. The absorption band of the compounds were observed in the order: NH2-3,5DABA (404 nm) > N02-3,5DABA (393 nm) > OH-3,5DABA (386 nm) > 3,5DABA (349 nm) > CH3-3,5DABA (347 nm).

Detection of Carbon, Sulfur, and Nitrogen Dioxide Pollutants with a 2D Ca12O12 Nanostructured Material.

In recent times, nanomaterials have been applied for the detection and sensing of toxic gases in the environment owing to their large surface-to-volume ratio and efficiency. CO2 is a toxic gas that is associated with causing global warming, while SO2 and NO2 are also characterized as nonbenign gases in the sense that when inhaled, they increase the rate of respiratory infections. Therefore, there is an explicit reason to develop efficient nanosensors for monitoring and sensing of these gases in the environment. Herein, we performed quantum chemical simulation on a Ca12O12 nanocage as an efficient nanosensor for sensing and monitoring of these gases (CO2, SO2, NO2) by employing high-level density functional theory modeling at the B3LYP-GD3(BJ)/6-311+G(d,p) level of theory. The results obtained from our studies revealed that the adsorption of CO2 and SO2 on the Ca12O12 nanocage with adsorption energies of -2.01 and -5.85 eV, respectively, is chemisorption in nature, while that of NO2 possessing an adsorption energy of -0.69 eV is related to physisorption. Moreover, frontier molecular orbital (FMO), global reactivity descriptors, and noncovalent interaction (NCI) analysis revealed that the adsorption of CO2 and SO2 on the Ca12O12 nanocage is stable adsorption, while that of NO2 is unstable adsorption. Thus, we can infer that the Ca12O12 nanocage is more efficient as a nanosensor in sensing CO2 and SO2 gases than in sensing NO2 gas.

Crystal structure of a chloride-bridged copper(II) dimer: piperazine-1,4-dium bis-(di-µ-chlorido-bis[(4-carboxypyridine-2-carboxyl-ato-κ2N,O2)chlorido-cuprate(II)].

Crystals of a new dimeric chloride-bridged cuprate(II) derived from pyridine-2,4-di-carb-oxy-lic acid were obtained solvothermally in the presence of piperazine and hydro-chloric acid. The crystal structure determination of the title salt, (C4H12N2)[Cu2(C7H4NO4)2Cl4], revealed one of the carboxyl groups of the original pyridine-2,4-di-carb-oxy-lic acid ligand to be protonated, whereas the other is deprotonated and binds together with the pyridine N atom to the CuII atom. The coordination environment of the CuII atom is distorted square-pyramidal. One of the chloride ligands bridges two metal cations to form a centrosymmetric dimer with two different Cu-Cl distances of 2.2632 (8) and 2.7853 (8) Å, whereby the longer distance is associated with the apical ligand. The remaining chloride ligand is terminal at one of the basal positions, with a distance of 2.2272 (9) Å. In the crystal, the dimers are linked by inter-molecular O-H⋯O hydrogen bonds, together with N-H⋯O and N-H⋯Cl inter-actions involving the centrosymmetric organic cation, into a three-dimensional supra-molecular network. Further but weaker C-H⋯O and C-H⋯Cl inter-actions consolidate the packing.