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In this work, the [2+2] photocycloaddition of carbonyl compounds with olefins, the Paterno-Buchi-type photoreaction, was performed in a flow microreactor under slug flow (two-phase flow) conditions...

With ever-evolving light-emitting diode (LED) technology, classical photochemical transformations are becoming accessible with more efficient and industrially viable light sources. In combination with a triplet sensitizer, we report the detailed exploration of [2 + 2] cycloadditions, in flow, of various maleic anhydride derivatives with gaseous ethylene. By the use of a flow reactor capable of gas handling and LED wavelength/power screening, an in-depth optimization of these reactions was carried out. In particular, we highlight the importance of matching the substrate and sensitizer triplet energies alongside the light source emission wavelength and power. Initial triplet-sensitized reactions of maleic anhydride were hampered by benzophenone’s poor absorbance at 375 nm. However, density functional theory (DFT) calculations predicted that derivatives such as citraconic anhydride have low enough triplet energies to undergo triplet transfer from thioxanthone, whose absorbance matches the LED emission at 375...

A typical (Paterno-Buchi type) organic photoreaction is examined in flow microreactors. Compared to the results achieved for simple one-layer flow modes, slug flow conditions (with the unreactive reagent composed of organic solution and water) achieve higher efficiency (conversion and yield) irrespective of the light source, concentration, and solvent. Furthermore, remarkably high productivity is also observed when only 5% water is added as an unreactive reagent. This method is broadly applicable for achieving highly efficient organic photoreactions not only in the laboratory, but also on the industrial scale.

Metal complex indicates the significant physical properties such as magnetism, electrical conductivity and an optical property due to the electronic interaction between the ligand molecule and the central metal ion. We have evaluated the magnetism of the metal complex by controlling the ligand field splitting, which is the energy splitting of the d-orbitals. The magnetic phenomenon of such compounds are realized as a result of the electronic state based on the transition metal coordination complexes, and which can be switched between high spin (HS) and low spin (LS), that is called a spin-crossover (SCO) phenomenon. Our group have been investigated the way how to control the spin state according to the concept of a molecular distortion. The five-coordinated metal complex ML5 has been experimentally confirmed to be a molecular distortion called the Berry pseudorotation (BPR). In the BPR process, both the axial and equatorial ligands can move at the same rate of increasing the angle between the other axial or equatorial ligands in five-coordinated metal complex. The classical BPR mechanism changes its molecular symmetry between two independent trigonal bipyramidals (TBPs) of D3h symmetry via a square pyramidal (SP) of C4v symmetry. The distortion parameters in the five-coordinated metal complexes τ5 are proposed in order to represent the distortion of the BPR process quantitatively. In this work, we predicted the possibility of the SCO phenomenon in intramolecular exchange mechanism through the BPR process in a five-coordinated metal complexes.

Metal complexes exhibit significant physical properties such as electrical conductivity, magnetism and optical properties. They can be controlled by changing the ligand field splitting of the d-orbital of the central metal ion. We have investigated the reversible spin crossover (SCO) phenomenon by changing the ligand field splitting in six-coordinated metal complexes ML6. In this study, we focused on the change of the spin states by uniaxial Jahn-Teller distortion in the case of an octahedral hexa-coordinated metal complexes ML6, involving two types of different ligand molecules. In addition, we have used DV-Xα and DVME methods in order to calculate the electronic states. In order to reproduce the effect of the Jahn-Teller distortion in the calculation, a uniaxial anisotropic distortion has been applied into the octahedral hexa-coordinate metal complex. The purpose of this research is to study the mechanism and phenomenon of the spin state changing by discussing the calculated electronic states of the spin crossover phenomenon.