Synthetic Control of the Excited‐State Dynamics and Circularly Polarized Luminescence of Fluorescent “Push–Pull” Tetrathia[9]helicenes

A series of fluorescent “push‐pull” tetrathia[9]helicenes based on quinoxaline (acceptor) fused with tetrathia[9]helicene (donor) derivatives was synthesized for control of the excited‐state dynamics and circularly polarized luminescence (CPL) properties. In this work, introduction of a quinoxaline onto the tetrathia[9]helicene skeleton induced the “push–pull” character, which was enhanced by further introduction of an electron‐releasing Me₂N group or an electron‐withdrawing NC group onto the quinoxaline unit (denoted as Me₂N‐QTTH and NC‐QTTH, respectively). These trends were successfully discussed in terms of by electrochemical measurements and density functional theory (DFT) calculations. As a consequence, significant enhancements in the fluorescence quantum yields (Φ_FL) were achieved. In particular, the maximum Φ_FL of Me₂N‐QTTH was 0.43 in benzene (NC‐QTTH: Φ_FL=0.30), which is more than 20 times larger than that of a pristine tetrathia[9]helicene (denoted as TTH; Φ_FL=0.02). These enhancements were also explained by kinetic discussion of the excited‐state dynamics such as fluorescence and intersystem crossing (ISC) pathways. Such significant enhancements of the Φ_FL values thus enabled us to show the excellent CPL properties. The value of anisotropy factor g_CPL (normalized difference in emission of right‐handed and left‐handed circularly polarized light) was estimated to be 3.0×10^?3 for NC‐QTTH.     

A photo-reagent system of benzimidazoline and Ru(bpy)3Cl2 to promote hexenyl radical cyclization and Dowd–Beckwith ring-expansion of α-halomethyl-substituted benzocyclic 1-alkanones

A combination of 2-aryl substituted 1,3-dimethyl-benzimidazolines (DMBIHs) and tris(2,2′-bipyridine)ruthenium(II) chloride, Ru(bpy)₃Cl₂ was used to promote photoinduced electron-transfer (PET) reactions of α-halomethyl-substituted benzocyclic 1-alkanones. This photo-reagent system stimulates free radical forming, cleavage of both carbon–bromine and carbon–chlorine bonds that are not activated by carbonyl groups. The resulting free radicals undergo 5-exo hexenyl cyclization as well as sequential cyclization and ring-expansion (Dowd–Beckwith) reactions to form radicals that abstract hydrogen atoms from the radical cation of DMBIH to yield the observed products. The results of a study of the effects of substituents located on the 2-aryl ring of DMBIH suggest that steric and hydrogen-bonding interactions influence the nature of the reaction pathways followed by the radical intermediates. PET reactions using an iridium complex and DMBIH were also investigated.     

Godement–Jacquet integrals on $$\mathrm{GL}(n,{\mathbf C})$$ GL ( n,C )

The Ramanujan Journal - We explicitly compute the complex archimedean part of the Godement–Jacquet zeta integral. We give a pair of a Schwartz–Bruhat function and a matrix coefficient...     

Null Wave Front and Ryu–Takayanagi Surface

The Ryu–Takayanagi formula provides the entanglement entropy of quantum field theory as an area of the minimal surface (Ryu–Takayanagi surface) in a corresponding gravity theory. There are some attempts to understand the formula as a flow rather than as a surface. In this paper, we consider null rays emitted from the AdS boundary and construct a flow representing the causal holographic information. We present a sufficient and necessary condition that the causal information surface coincides with Ryu–Takayanagi surface. In particular, we show that, in spherical symmetric static spacetimes with a negative cosmological constant, wave fronts of null geodesics from a point on the AdS boundary become extremal surfaces and therefore they can be regarded as the Ryu–Takayanagi surfaces. In addition, from the viewpoint of flow, we propose a wave optical formula to calculate the causal holographic information.     

Diameter dependent electron transfer in supramolecular nanohybrids of (6,5)- or (7,6)-enriched semiconducting SWCNT as donors and fullerene as acceptor

Diameter dependent electron donor behavior of (6,5)- and (7,6)-enriched semiconducting SWCNT is proved by constructing supramolecular nanohybrids with pyrene functionalized electron acceptor, fullerene, and the subsequent photocatalytic/ photoelectrochemical processes.     

Quantum spin fluctuations in the spin-liquid state of Tb?Ti?O?

Neutron scattering experiments on a polycrystalline sample of the frustrated pyrochlore magnet Tb(2)Ti(2)O(7), which does not show any magnetic order down to 50 mK, have revealed that it shows condensation behavior below 0.4 K from a thermally fluctuating paramagnetic state to a spin-liquid ground state with quantum spin fluctuations. Energy spectra change from quasielastic scattering to a continuum with a double-peak structure at energies of 0 and 0.8 K in the spin-liquid state. Specific heat shows an anomaly at the crossover temperature.     

Electrochemical detection for dynamic analyses of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device

This report describes the electrochemical detection of a redox component in droplets using a local redox cycling-based electrochemical (LRC-EC) chip device consisting of 256 sensors. The time-course analyses showed that the redox compound in the droplet was dynamically changed during droplet evaporation or mass transfer through a water/oil interface.     

Preparation and structural control of metal coordination-assisted supramolecular architectures of porphyrins. Nanocubes to microrods

We have successfully prepared metal coordination-assisted porphyrin assemblies such as nanocubes, nanorods and microrods by controlling the synthetic conditions. The internal structures and lifetimes of the excited states are also quantitatively discussed.     

Diastereoselectivity at chiral metal center of half-sandwich-type ruthenium complexes with planar-chiral cyclopentadienyl ligands in multiple ligand transfer reaction

The triple ligand transfer reaction between planar-chiral cyclopentadienyl-ruthenium complexes [Cp′Ru(NCMe)₃][PF₆] (1) (Cp′ = 1-(COOR²)-2-Me-4-R¹C₅H₂; R¹ = Me, Ph, t-Bu) and iron complexes CpFe(CO)(L)X (2) (L = PMe₃, PMe₂Ph, PMePh₂, PPh₃; X = I, Br) resulted in the formation of metal-centered chiral ruthenium complexes Cp′Ru(CO)(L)X (3) in moderate yields with diastereoselectivities of up to 68% de. The configurations of some major diastereomers were determined to be by X-ray crystallography. The diastereoselectivity of 3 was under kinetic control and not affected by the steric effect of the substituents on the Cp′ ring of 1 and the phosphine of 2. Although the double ligand transfer reaction between [Cp′Ru{P(OMe)₃}(NCMe)₂][PF₆] (7) and CpFe(CO)₂X (8) produced Cp′Ru{P(OMe)₃}(CO)X (9), the selectivity at the ruthenium center was low.