Synthesis and electronic properties of meso-tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes

meso-Tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes were synthesized and their electronic absorption and magnetic circular dichroism (MCD) spectra discussed based on TD-DFT molecular orbital (MO) calculations. Nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations were also carried out for metal-free (and phosphorus) tetrabenzoporphyrins in order to discuss the aromaticity and flow of electrons in the molecule.

Reduction of Orbital Space for Molecular Orbital Calculations with Quantum Computation Simulator for Educations

Recently, the molecular orbital (MO) calculations with quantum computations (QCs) have attracted considerable interest. The cost of QCs highly depends on the number of qubits even on quantum simulators. The reduction of MO space can thus be a crucial issue for the practical applicability of MO-QC. Besides the frozen-core restriction for the occupied MO space, we have used the pseudo-natural orbital derived from the second-order M{\o}ller-Plesset perturbation (MP2) theory for the virtual MO space. A preliminary test on the LiH molecule (STO-3G basis) showed acceleration by a factor larger than 500 for MO-QC with the Blueqat simulator, where the required time was 72 s per solution. Simulations of MO-QC may be used as practical teaching materials in classes.

Reduction of Orbital Space for Molecular Orbital Calculations with Quantum Computation Simulator for Educations

Recently, the molecular orbital (MO) calculations with quantum computations (QCs) have attracted considerable interest. The cost of QCs highly depends on the number of qubits even on quantum simulators. The reduction of MO space can thus be a crucial issue for the practical applicability of MO-QC. Besides the frozen-core restriction for the occupied MO space, we have used the pseudo-natural orbital derived from the second-order M{\o}ller-Plesset perturbation (MP2) theory for the virtual MO space. A preliminary test on the LiH molecule (STO-3G basis) showed acceleration by a factor larger than 500 for MO-QC with the Blueqat simulator, where the required time was 72 s per solution. Simulations of MO-QC may be used as practical teaching materials in classes.

SPECTROSCOPICALLY AND/OR STRUCTURALLY INTRIGUING PHTHALOCYANINES AND RELATED COMPOUNDS. PART 1. MONOMERIC SYSTEMS

The first part of the series of review papers on the properties of some synthetically and spectroscopically interesting studies of our group for the period 2007-2017 is presented. In particular, examples are shown on the analysis of spectroscopic data in conjunction with molecular orbital (MO) calculations. We have used mainly electronic absorption and natural and magnetic circular dichroism (CD and MCD) spectroscopic techniques, with occasional use of fluorescence, phosphorescence, and time-resolved EPR. Not only the spectra of (4n + 2)π systems, but also some 4nπ anti-aromatic systems are theoretically analyzed, which helps the reader to learn how to interprete the spectral data. In the first part and the second part of this review monomer systems are considered, and in the third - trimeric and tetrameric systems. <span style="opacity: 0;"> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . </span>

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

An efficient synthesis methodology for a series of tetrazolo[1,5-a]pyrimidines substituted at the 5- and 7-positions from the cyclocondensation reaction [CCC + NCN] was developed. The NCN corresponds to 5-aminotetrazole and CCC to β-enaminone. Two distinct products were observed in accordance with the β-enaminone substituent. When observed in solution, the compounds can be divided into two groups: (a) precursor compounds with R = CF3 or CCl3, which leads to tetrazolo[1,5-a]pyrimidines in high regioselectivity with R at the 7-position of the heterocyclic ring; and (b) precursor compounds with R = aryl or methyl, which leads to a mixture of compounds, tetrazolo[1,5-a] pyrimidines (R in the 5-position of the ring) and 2-azidopyrimidines (R in the 4-position of the ring), which was attributed to an equilibrium of azide–tetrazole. In the solid state, all compounds were found as 2-azidopyrimidines. The regiochemistry of the reaction and the stability of the products are discussed on the basis of the data obtained by density functional theory (DFT) for energetic and molecular orbital (MO) calculations.

Computer-Aided Insight into the Relative Stability of Enamines

Venerable aldol, Michael, and Mannich reactions have undergone a renaissance in the past fifteen years, as a consequence of the development of direct organocatalytic versions, mediated by chiral amines. Chiral enamines are key intermediates in these reactions. This review focuses on the formation of enamines from secondary amines and their relative thermodynamic stability, as well as on the reverse reactions (hydrolysis). Experimental results and predictions based on MO calculations are reviewed to show which enamine forms may predominate in the reaction medium and to compare several secondary amines as organocatalysts.1 Introduction2 Relative Stability of Enamines as Determined Experimentally3 Pyrrolidine Enamines4 Enamines of the Jørgensen–Hayashi Catalyst5 Proline Enamines6 Free Enthalpies and Polar Solvent Effects7 Comparison of Organocatalysts8 Summary and Outlook9 Appendix

NQR and X-ray crystal structure studies of cadmium halide complexes: [C(NH2)3]CdI3 and [4-ClC6H5NH3]3CdBr5

The crystal structures of [C(NH2)3]CdI3(1) and [4-ClC6H5NH3]3CdBr5(2) have been determined at 100 K: monoclinic,Cc,a= 828.75(3) pm,b= 1615.31(5) pm,c= 810.64(3) pm, andβ= 106.5820(10)° for1; monoclinic,P21/c,a= 1486.93(5) pm,b= 794.31(3) pm,c= 2290.59(7) pm, andβ= 99.6830(10)° for2. The structure of1has an infinite chain of anions consisting of [CdI4] tetrahedra sharing two corners. The structure of2has an infinite chain of anions consisting of [CdBr6] octahedra sharing two corners in cispositions. In both structures, isolated cations are connected to the anion chains through weak hydrogen bonds Cd–X···H to result in three-dimensional network structures. In accordance with the crystal structures, three127I (m= ±1/2 ↔m= ±3/2), five81Br, and three35Cl nuclear quadrupole resonance (NQR) lines were observed for1and2. The NQR spectra reflect the anion chain structures and their weak hydrogen bonds. The MO calculations of the models [Cd5I16]6–for1and [Cd3Br16]10–for2estimate only about half the values for the NQR frequencies but give accurate electric field gradient directions.