scholarly journals Orientations and water dynamics of photoinduced secondary charge-separated states for magnetoreception by cryptochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Misato Hamada ◽  
Tatsuya Iwata ◽  
Masaaki Fuki ◽  
Hideki Kandori ◽  
Stefan Weber ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Charge Separation ◽  
Energy Gap ◽  
Electron Tunneling ◽  
Weak Field ◽  
Magnetic Compass ◽  
Water Dynamics ◽  
Electronic Coupling ◽  
Triplet Energy ◽  
Time Resolved

AbstractIn the biological magnetic compass, blue-light photoreceptor protein of cryptochrome is thought to conduct the sensing of the Earth’s magnetic field by photoinduced sequential long-range charge-separation (CS) through a cascade of tryptophan residues, WA(H), WB(H) and WC(H). Mechanism of generating the weak-field sensitive radical pair (RP) is poorly understood because geometries, electronic couplings and their modulations by molecular motion have not been investigated in the secondary CS states generated prior to the terminal RP states. In this study, water dynamics control of the electronic coupling is revealed to be a key concept for sensing the direction of weak magnetic field. Geometry and exchange coupling (singlet–triplet energy gap: 2J) of photoinduced secondary CS states composed of flavin adenine dinucleotide radical anion (FAD−•) and radical cation WB(H)+• in the cryptochrome DASH from Xenopus laevis were clarified by time-resolved electron paramagnetic resonance. We found a time-dependent energetic disorder in 2J and was interpreted by a trap CS state capturing one reorientated water molecule at 120 K. Enhanced electron-tunneling by water-libration was revealed for the terminal charge-separation event at elevated temperature. This highlights importance of optimizing the electronic coupling for regulation of the anisotropic RP yield on the possible magnetic compass senses.

Ternary donor–acceptor phosphine oxide hosts with peculiar high energy gap for efficient blue electroluminescence

2015 ◽  
Vol 3 (36) ◽  
pp. 9469-9478 ◽  
Author(s):  
Mingzhi Sun ◽  
Liping Zhu ◽  
Wenjing Kan ◽  
Ying Wei ◽  
Dongge Ma ◽  
...  
Keyword(s):  
Phosphine Oxide ◽  
Energy Gap ◽  
High Energy ◽  
Electronic Coupling ◽  
Triplet Energy ◽  
Donor Acceptor

A triangle-shaped D–A–A molecule PCImbPO with unusually high triplet energy of 3.0 eV, enhanced D–A electronic coupling and separated FMO and triplet locations is described.

Near-infrared luminescent Sn(IV) complexes of N-confused tetraphenylporphyrin: Effect of axial anion coordination

2015 ◽  
Vol 19 (01-03) ◽  
pp. 361-371 ◽  
Author(s):  
Arghya Basu ◽  
Motoki Kitamura ◽  
Shigeki Mori ◽  
Masatoshi Ishida ◽  
Yongshu Xie ◽  
...  
Keyword(s):  
Near Infrared ◽  
Energy Gap ◽  
Theoretical Calculations ◽  
Crystallographic Analysis ◽  
Molecular Structures ◽  
Triplet Energy ◽  
Time Resolved ◽  
Axial Coordination ◽  
Anion Coordination ◽  
Axial Ligands

Novel tin(IV) halo complexes of an N-confused tetraphenylporphyrin with different axial ligands have been synthesized and characterized by various spectroscopic methods including X-ray crystallographic analysis. The molecular structures of the dichloro and dibromo derivatives possess perfect octahedral geometries, which are nearly comparable to the corresponding regular porphyrin complexes. In contrast, the iodide/triiodide complex obtained by a same reaction manner, demonstrated that the tin(IV) cation is slightly displaced towards axially coordinated iodide anion, giving rise to the different electronic structure due to the tautomeric form of N-confused porphyrin ligand. These structural differences reflected to the distinct photophysical and electrochemical properties. The Sn(IV) complexes are near IR luminescent, however the unsymmetrical axial coordination of iodide and triiodide anions in the tin(IV) N-confused porphyrin complex allows, in particular, the longer emission lifetimes and a smaller singlet-triplet energy gap, which were investigated by steady-state and time-resolved spectroscopies as well as theoretical calculations.

scholarly journals The Photophysical Properties of Triisopropylsilyl-ethynylpentacene—A Molecule with an Unusually Large Singlet-Triplet Energy Gap—In Solution and Solid Phases

Chemistry ◽  
2020 ◽  
Vol 2 (2) ◽  
pp. 545-564
Author(s):  
Fabio A. Schaberle ◽  
Carlos Serpa ◽  
Luis G. Arnaut ◽  
Andrew D. Ward ◽  
Joshua K. G. Karlsson ◽  
...  
Keyword(s):  
Energy Gap ◽  
Photophysical Properties ◽  
Solute Concentration ◽  
Fluorescence Yield ◽  
Triplet States ◽  
Dilute Solution ◽  
Excimer Emission ◽  
Triplet Energy ◽  
Time Resolved ◽  
Singlet Exciton

The process of singlet-exciton fission (SEF) has attracted much attention of late. One of the most popular SEF compounds is TIPS-pentacene (TIPS-P, where TIPS = triisopropylsilylethynyl) but, despite its extensive use as both a reference and building block, its photophysical properties are not so well established. In particular, the triplet state excitation energy remains uncertain. Here, we report quantitative data and spectral characterization for excited-singlet and -triplet states in dilute solution. The triplet energy is determined to be 7940 ± 1200 cm−1 on the basis of sensitization studies using time-resolved photoacoustic calorimetry. The triplet quantum yield at the limit of low concentration and low laser intensity is only ca. 1%. Self-quenching occurs at high solute concentration where the fluorescence yield and lifetime decrease markedly relative to dilute solution but we were unable to detect excimer emission by steady-state spectroscopy. Short-lived fluorescence, free from excimer emission or phosphorescence, occurs for crystals of TIPS-P, most likely from amorphous domains.

STABLE hc/e VORTICES IN SUPERCONDUCTORS WITH SPIN-CHARGE SEPARATION

1992 ◽  
Vol 06 (05n06) ◽  
pp. 509-526
Author(s):  
Subir Sachdev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Normal State ◽  
Phenomenological Model ◽  
Charge Separation ◽  
Cuprate Superconductors ◽  
Superconducting Phase ◽  
Low Energy ◽  
Large N ◽  
Normal State Properties

A phenomenological model, F, of the superconducting phase of systems with spin-charge separation and antiferromagnetically induced pairing is studied. Above Hc1, magnetic flux can always pierce the superconductor in vortices with flux hc/2e, but regimes are found in which vortices with flux hc/e are preferred. Little-Park and other experiments, which examine periodicities with a varying magnetic field, always observe a period of hc/2e. The low energy properties of a symplectic large-N expansion of a model of the cuprate superconductors are argued to be well described by F. This analysis and some normal state properties of the cuprates suggest that hc/e vortices should be stable at the lowest dopings away from the insulating state at which superconductivity first occurs.

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