Sensitization with dyes is the most promising option to narrow the band gap and improve visible-light absorption of TiO 2 . As ideal structure and reaction models of TiO 2 , titanium oxo clusters (TOCs) with exact crystal structure are beneficial for further understanding the structure−property relationship of TiO 2 . Most reports mainly focus on the synthesis and properties of TOCs, but research on the band-gap tuning of TOCs at the large range of 3.7−2.0 eV by chromophore ligands (CLs) has been lacking. Herein, six new Ti 6 -core-based TOCs (Ti 6 -TOCs) were successfully synthesized by using CLs in a simple and general approach. Each Ti 6 -TOC structure contains two Ti 3 (μ 3 -O) units featuring a flat or pyramidal mode as building blocks. Five Ti 6 -core structure types were present among the six Ti 6 -TOCs, which enriched the family of hexanuclear TOCs. To be noted, the band-gap values were tuned at a wide range of 3.41−1.98 eV by controlling the type and number of the CLs 2-hydroxypyridine, salicylaldoxime, and catechol in the structure. Density functional theory calculation revealed that the lowest-energy bands of these Ti 6 -TOCs are attributed to the CL-to-TiO core charge-transfer bands. This work provides a precise and wide-ranged band-gap tuning method for TOCs. Additionally, the six Ti 6 -TOCs exhibit good photocurrent response.

The pairing of transition metal catalysis with the reagent Selectfluor (F-TEDA-BF4) has attracted considerable attention due to its utility in myriad C-C and C-heteroatom bond-forming reactions. However, little mechanistic information is available for Selectfluor-mediated transition metal-catalyzed reactions and controversy surrounds the precise role of Selectfluor in these processes. We present herein a systematic investigation of homogeneous Au-catalyzed oxidative C-O bond-forming reactions using density functional theory calculations. Currently, Selectfluor is thought to serve as an external oxidant in Au(I)/Au(III) catalysis. However, our investigations suggest that these reactions follow a newly proposed mechanism in which Selectfluor functions as an electrophilic fluorinating reagent involved in a fluorination/defluorination cycle. We have also explored Selectfluor-mediated gold-catalyzed homocoupling reactions, which, when cyclopropyl propargylbenzoate is used as a substrate, lead to an unexpected byproduct.

In this work, kinetic studies on HEH 2 , 2-benzylmalononitrile, 2-benzyl-1 H -indene-1,3(2 H )-dione, 5-benzyl-2,2-dimethyl-1,3-dioxane-4,6-dione, 5-benzyl-1,3-dimethylpyrimidine-2,4,6(1 H ,3 H ,5 H )-trione, 2-(9 H -fluoren-9-yl)malononitrile, ethyl 2-cyano-2-(9 H -fluoren-9-yl)acetate, diethyl 2-(9 H -fluoren-9-yl)malonate, and the derivatives (28 XH 2 ) releasing two hydrogen atoms were carried out. The thermokinetic parameters Δ G ⧧ ° of 28 dihydrogen donors (XH 2 ) and the corresponding hydrogen atom acceptors (XH • ) in acetonitrile at 298 K were determined. The abilities of releasing two hydrogen atoms for these organic dihydrogen donors were researched using their thermokinetic parameters Δ G ⧧ °(XH 2 ), which can be used not only to compare the H-donating ability of different XH 2 qualitatively and quantitatively but also to predict the rates of HAT reactions. Predictions of rate constants for 12 HAT reactions using thermokinetic parameters were determined, and the reliabilities of the predicted results were also examined.

The selective fluorination of aromatic compounds with Selectfluor has been studied theoretically. The structural and energetic features of p complexes of substituted benzenes with Selectfluor are investigated, and the fluorine bond (F/p) has been found to make an important contribution to the stabilization of the p complexes. Our calculations indicate that the SET mechanism, which involves one electron transfer from the aromatic substrate (D) to Selectfluor (A), is preferred over the S N 2 mechanism.The analysis of the minimum energy path (MEP) suggests that the DABCO moiety of Selectfluor seems to take an active role in the fluorination of aromatic compounds with Selectfluor. In addition, a two-state model analysis, as well as the characteristics of avoiding crossing between the DA and D + A À states of benzene/Selectfluor are addressed to obtain deep insight into the features of the SET mechanism.