Chemistry remains an experimental science. The theory of chemical bonding leaves much to be desired. Yet, the past 20 years have been marked by a fruitful symbiosis of organic chemistry and molecular orbital theory. Of necessity this has been a marriage of poor theory with good experiment. Tentative conclusions have been arrived a t on the basis of theories which were such a patchwork on approximations that they appeared to have no right to work; yet, in the hands of clever experimentalists, these ideas were transformed into novel molecules with unusual properties. In the same way, by utilizing the most simple but fundamental concepts of molecular orbital theory we have in the past 3 years been able to rationalize and predict the stereochemical course of virtually every concerted organic reaction.' In our work we have relied on the most basic ideas of molecular orbital theory-the concepts of symmetry, overlap, interaction, bonding, and the nodal structure of wave functions. The lack of numbers in our discussion is not a weakness-it is its greatest strength. Precise numerical values would have to result from some specific sequence of approximations. But an argument from first principles or symmetry, of necessity qualitative, is in fact much stronger than the deceptively authoritative numerical result. For, if the simple argument is true, then any approximate method, as well as the now inaccessible exact solution, must obey it. The simplest description of the electronic structure of a stable molecule is that i t is characterized by a finite band of doubly occupied electronic levels, called bonding orbitals, separated by a gap from a corresponding band of unoccupied, antiboding levels as well as a continuum of higher levels. The magnitude of the gap may range from 40 kcal/mole for highly delocalized, large aromatic systems to 250 kcal/mole for saturated hydrocarbons. It should be noted in context that socalled nonbonding electrons of heteroatoms are in fact bonding. Consider a simple reaction of two molecules to give a third species, proceeding in a nonconcerted manner through a diradical intermediate I. A + B + [I] + C

The Conservation of Orbital Symmetry (福井謙一とフロンティア軌導理論) -- (参考論文)

In this work, we studied the structural, optical and nonlinear optical properties and UV–visible absorption spectrum of the heteroleptic bis-cyclometalated iridium(III) complex (tfmppy)2Ir(pic) recently synthesized with tfmppy = 5-trifluoromethyl-2-phenylpyridine and pic = picolinate. The calculations were performed by means of density functional theory (DFT) and time-dependent density functional (TD-DFT) methods using four functionals B3LYP, PBE0, CAM-B3LYP and M06-2X. Calculated geometric parameters agree with the experimental data. CAM-B3LYP and M06-2X lower the HOMO energy level and give a large energy gaps compared with B3LYP and PBE0. The four functionals show that LUMO is delocalized over $$ \pi_{\text{ppy}}^{ * } $$
 orbital, and HOMO is contributed by $$ \pi_{\text{ppy}} $$
 and dIr orbitals. The studied complex gets a remarkably large first-order NLO response. B3LYP would provide good estimates of the energy gap and shows the strongest values of the first hyperpolarizabilities βHRS; M06-2X and CAM-B3LYP functionals overestimate the gaps and lower βHRS values. PBE0 and B3LYP spectra agree better with the experimental spectrum in the visible region, while CAM-B3LYP and M06-2X are more accurate in UV-C region. Natural transition orbital analysis shows that the weak band observed at 468 nm corresponds to MLCT/LLCT charge transfer transitions and the intense band observed at 270 nm is mainly assigned to intra-ligand state.

Structural, optical and nonlinear optical properties and TD-DFT analysis of heteroleptic bis-cyclometalated iridium(III) complex containing 2-phenylpyridine and picolinate ligands

Sarain A is a complex macrocyclic marine alkaloid extracted from sponges of the order Haplosclerida. It is likely that this alkaloid shares a common origin with manzamine alkaloids, also extracted from sponges of the same order. In this paper, new concepts concerning this origin are presented and constitute the basis for a synthetic strategy. A preliminary evaluation of this strategy is presented and leads, as a first result, to a five-step access to the bicyclic intermediate 43. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

First model reactions towards the synthesis of Sarain A core skeleton based upon a biogenetic scenario.

Spectroscopic (UV-vis, FT-IR, FT-Raman, and NMR) analysis, structural benchmarking, molecular properties, and the in-silico cerebral anti-ischemic activity of 2-amino-6-ethoxybenzothiazole

Synthesis and DFT calculations of linear and nonlinear optical responses of novel 2-thioxo-3-N,(4-methylphenyl) thiazolidine-4 one

First theoretical study of linear and nonlinear optical properties of diphenyl ferrocenyl butene derivatives

Molecular structure, linear and nonlinear optical properties of some cyclic phosphazenes: A theoretical investigation

In this work, we studied the structural, optical, nonlinear optical properties , absorption spectra and phosphorescence properties of four cyclometalated heteroleptic iridium complexes [Ir(dFNppy)2(PPh3)L] with dFNppy = 5-nitro-2-(2′,4′-difluorophenylpyridyl, PPh3 = triphenylphosphine, L = Cl− (1), NCS− (2), NCO− (3) and N3− (4) using DFT and TD-DFT methods. The electronic and geometrical structures of the S0 and T1 have been studied and compared. Experimental absorption bands were assigned on the basis of natural transition orbitales, and a good agreement with experience has been obtained. Phosphorescence wavelengths of the four complexes were calculated with vertical and adiabatic methods. Further, linear optical properties (mean polarizability $$\left\langle \alpha \right\rangle$$, anisotropy polarizability $$\left| \alpha \right|$$), the static first hyperpolarizabilities electric-field-induced second harmonic generation $$\beta_{//} \left( { - 2\omega ;\omega ,\omega } \right)$$ and the hyper-Rayleigh scattering (HRS) first hyperpolarizability $$\beta_{\text{HRS}} \left( { - 2\omega ;\omega ,\omega } \right)$$), and the depolarization ratio DR of these complexes are calculated by DFT with PBE0 functional in order to understand nonlinear optical properties. Higher polarizability $$(\alpha )$$ and first hyperpolarizabilities $$(\beta )$$ of these complexes are obtained. It is also observed an inverse correlation between the predicted β value and the HOMO–LUMO energy difference (Δe).

Theoretical study of geometric, optical, nonlinear optical, UV–Vis spectra and phosphorescence properties of iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl

Djebar Hadji

Papers

Structural, optical and nonlinear optical properties and TD-DFT analysis of heteroleptic bis-cyclometalated iridium(III) complex containing 2-phenylpyridine and picolinate ligands

Synthesis and DFT calculations of linear and nonlinear optical responses of novel 2-thioxo-3-N,(4-methylphenyl) thiazolidine-4 one

First theoretical study of linear and nonlinear optical properties of diphenyl ferrocenyl butene derivatives

Molecular structure, linear and nonlinear optical properties of some cyclic phosphazenes: A theoretical investigation

Theoretical study of geometric, optical, nonlinear optical, UV–Vis spectra and phosphorescence properties of iridium(III) complexes based on 5-nitro-2-(2′,4′-difluorophenyl)pyridyl