Role of hydrogen bonding interactions within of the conformational preferences of calix[n = 4,6,8]arene: DFT and QTAIM analysis.

Understanding the interactions of the cage molecules with a variety of invited molecules is getting very important. But, the hydrogen bonds can also play a crucial role in the interaction phenomenon. In this work, natural population analysis (NPA), chemical shifts, and atom in molecules (AIM) analysis have been used to identify the role of hydrogen bonds in the stability of CX[n] molecules. According to our calculation, the 13C NMR spectra are also sensitive to the nature of hydrogen bonds. We note that the DFT calculations have reproduced with a very good agreement, the experimentally observed chemical shifts of CX[4].

New zinc phthalocyanine derivatives for nitrogen dioxide sensors: A theoretical optoelectronic investigation.

Zinc-phthalocyanines ZnPc derivatives including quinoleinoxy groups have been studied through DFT calculations. The most stable geometries were characterized for the unsubstituted to the tetra substituted ZnPcs. The energy gap decreased from 2.146 eV for ZnPc to 2.050 eV for ZnPcR4, in agreement with the experimental trend, and indicating the reliability of the electrochemical evaluation of LUMO and HOMO energy levels. Optical transitions computed at the CAM-B3LYP-D3 with triple zeta basis sets were found to be in good agreement with experimental values for both the B and Q bands. Subsequently, structures were also characterized for NO2 adsorbed complexes, in order to assess the potential role of ZnPc as a NO2 sensor. A clear sigma bonding chemisorption of NO2 on Zn atom is observed for all derivatives, followed by a charge transfer from the π Pc conjugated system to the Zn-NO2 moiety. More importantly, after NO2 chemisorption on ZnPc derivative a remarkable red-shift is observed in the optical spectra, particularly for NO2/ZnPcR4 complex, thus offering a good index to detect the binding of NO2. The optical spectra and the vibrational spectra can therefore be used to detect the presence of NO2 and ZnPc derivatives show appropriate properties to constitute good NO2 sensors.

Crystal structure of 4,4-di-bromo-1-(3,4-di-meth-oxy-phen-yl)-2-aza-buta-1,3-diene-1-carbo-nitrile.

The title compound, C12H10Br2N2O2, represents an example of a planar π-con-jugated 2-aza-butadiene mol-ecule, which is both an inter-esting starting material for further organic transformations and a potential ligand in organometallic coordination chemistry. Its metric mol-ecular parameters are typical for the family of 2-aza-buta-1,3-dienes not substituted at the (CH) 3-position. In the crystal, the almost planar (r.m.s. deviation = 0.0658 Å) aza-diene mol-ecules form one-dimensional double-wide ribbons through inter-molecular halogen bonds (C-Br⋯O and C-Br⋯Br-C), which then stack in a slipped manner through weak C-H⋯Br and π-π inter-actions to generate a three-dimensional network.