Chlorosilanes are versatile reagents in organic synthesis and material science.Amild pathway is nowreported for the quantitative conversion of hydrosilanes to silyl chlorides under visible-light irradiation using neutral eosin Ya s ah ydrogen-atom-transfer photocatalyst and dichloromethane as ac hlorinating agent. Stepwise chlorination of di-and trihydrosilanes was achieved in ah ighly selective fashion assisted by continuous-flowm icro-tubing reactors.T he ability to access silyl radicals using photocatalytic SiÀHa ctivation promoted by eosin Yoffers new perspectives for the synthesis of valuable silicon reagents in aconvenient and green manner.

Gold nanoparticle modifications for TiO2 (Au/TiO2) can extend the absorption wavelength from UV to visible (Vis) and enhance the photocatalytic performance, thus fueling increasing attention as an emerging photocatalysis strategy. To explore the plasmon-enhanced photocatalytic mechanism and directly unveil the intrinsic properties of Au/TiO2, the decay kinetics of photoelectrons upon UV (355 nm) or Vis (532 nm) excitation are monitored by means of nanosecond time-resolved infrared spectroscopy, which is a unique tool offering observations without interference of the holes. Under UV irradiation, the longer lifetime of photoelectrons observed in Au/TiO2 compared to that in bare TiO2 provides unambiguous evidence for the enhanced charge separation by AuNPs. Under Vis irradiation, the long-lived (hundreds of microseconds) electrons produced by injection from AuNPs into TiO2 upon plasmon excitation are here detected for the first time. Moreover, the effects of TiO2 phase composition and the amount of AuNPs loading on the decay kinetics of long-lived photoelectrons are examined.

The triplet metal to ligand charge transfer (3MLCT) luminescence of ruthenium (II) polypyridyl complexes offers attractive imaging properties, specifically towards the development of sensitive and structure-specific DNA probes. However, rapidly-deactivating dark state formation may compete with 3MLCT luminescence depending on different DNA structures. In this work, by combining femtosecond and nanosecond pump-probe spectroscopy, the 3MLCT relaxation dynamics of [Ru(phen)2(dppz)]2+ (phen = 1,10-phenanthroline, dppz = dipyridophenazine) in two iconic G-quadruplexes has been scrutinized. The binding modes of stacking of dppz ligand on the terminal G-quartet fully and partially are clearly identified based on the biexponential decay dynamics of the 3MLCT luminescence at 620 nm. Interestingly, the inhibited dark state channel in ds-DNA is open in G-quadruplex, featuring an ultrafast picosecond depopulation process from 3MLCT to a dark state. The dark state formation rates are found to be sensitive to the content of water molecules in local G-quadruplex structures, indicating different patterns of bound water. The unique excited state dynamics of [Ru(phen)2(dppz)]2+ in G-quadruplex is deciphered, providing mechanistic basis for the rational design of photoactive ruthenium metal complexes in biological applications.

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Phosphorothioate (PS) modified oligonucleotides (S-DNA) naturally exist in bacteria and archaea genome and are widely used as an antisense strategy in gene therapy. However, the introduction of PS as a redox active site may trigger distinct UV photoreactions. Herein, by time-resolved spectroscopy, we observe that 266 nm excitation of S-DNA d(A ps ) 20 and d(A ps A) 10 leads to direct photoionization on the PS moiety to form hemi-bonded -P-S∴S-P-radicals, in addition to A base ionization to produce A +• /A(-H) • . Fluorescence spectroscopy and global analysis indicate that an unusual charge transfer state (CT) between the A and PS moiety might populate in competition with the common CT state among bases as key intermediate states responsible for S-DNA photoionization. Significantly, the photoionization bifurcating to PS and A moieties of S-DNA is discovered, suggesting that the PS moiety could capture the oxidized site and protect the remaining base against ionization lesion, shedding light on the understanding of its existence in living organisms.