Role of l→aπ Transitions in Spin—Orbit Coupling of Aromatic Amines: Phosphorescence of Aniline and its N‐Alkyl Derivatives

Triazine and Fused Thiophene-Based Donor-Acceptor Type Semiconducting Conjugated Polymer for Enhanced Visible-Light-Induced H2 Production

Conjugated polymers have attracted significant attention in the field of photocatalysis due to their exceptional properties, including versatile optimization, cost-effectiveness, and structure stability. Herein, two conjugated porous polymers, PhIN-CPP and ThIN-CPP, based on triazines, were meticulously designed and successfully synthesized using benzene and thiophene as building blocks. Based on UV diffuse reflection spectra, the photonic band gaps of PhIN-CPP and ThIN-CPP were calculated as 2.05 eV and 1.79 eV. The PhIN-CPP exhibited a high hydrogen evolution rate (HER) of 5359.92 μmol·g-1·h-1, which is 10 times higher than that of Thin-CPP (538.49 μmol·g-1·h-1). The remarkable disparity in the photocatalytic performance can be primarily ascribed to alterations in the band structure of the polymers, which includes its more stable benzene units, fluffier structure, larger specific surface area, most pronounced absorption occurring in the visible region and highly extended conjugation with a high density of electrons. The ΔEST values for PhIN-CPP and ThIN-CPP were calculated as 0.79 eV and 0.80 eV, respectively, based on DFT and TD-DFT calculations, which revealed that the incorporation of triazine units in the as-prepared CMPs could enhance the charge transfer via S1 ↔ T1 and was beneficial to the photocatalytic decomposition of H2O. This study presents a novel concept for developing a hybrid system for preparation of H2 by photocatalysis with effectiveness, sustainability, and economy.

Design, Fabrication, and Mechanism of Nitrogen-Doped Graphene-Based Photocatalyst

Solving energy and environmental problems through solar-driven photocatalysis is an attractive and challenging topic. Hence, various types of photocatalysts have been developed successively to address the demands of photocatalysis. Graphene-based materials have elicited considerable attention since the discovery of graphene. As a derivative of graphene, nitrogen-doped graphene (NG) particularly stands out. Nitrogen atoms can break the undifferentiated structure of graphene and open the bandgap while endowing graphene with an uneven electron density distribution. Therefore, NG retains nearly all the advantages of original graphene and is equipped with several novel properties, ensuring infinite possibilities for NG-based photocatalysis. This review introduces the atomic and band structures of NG, summarizes in situ and ex situ synthesis methods, highlights the mechanism and advantages of NG in photocatalysis, and outlines its applications in different photocatalysis directions (primarily hydrogen production, CO₂ reduction, pollutant degradation, and as photoactive ingredient). Lastly, the central challenges and possible improvements of NG-based photocatalysis in the future are presented. This study is expected to learn from the past and achieve progress toward the future for NG-based photocatalysis.

Preparation and Electronic Property Investigation of Zinc(II)-Schiff Base Complexes in the Confined Space

Metal-Schiff base complexes have attracted continued research interest regarding their intriguing and useful features, while the electronic properties of these complexes in the confined space have not been sufficiently addressed in previous studies. In this work, a new zinc(II)-Schiff base complex bis(N-dodecyl salicylideneiminato)Zn(II) (1) was synthesized and subsequently loaded in an inorganic solid host. A large red shift (~40 nm) of the absorption onset was recorded, when the microenvironment of1changed from the solvent ethanol to the inorganic solid medium, evidencing the confined space effect. The marked shift of the absorption onset was associated with a band-gap reduction between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Theoretical calculation results showed that the confined space effect is distance dependent and exerts a more profound influence on the HOMO than the LUMO within an effective distance range. An initial study implied that the confined space effect is also accompanied with the electron density variation.

N-hetero atomic effect on the photophysics of 2,2'-dipyridylketone

Emission characteristics of 2,2'-dipyridylketone (DPK) have been studied in the rigid glass matrices of ethanol (EtOH) and methyl cyclohexane (MCH) at 77 K. As in the case of the aromatic analogue benzophenone (BOP), DPK is found to exhibit only phosphorescence emission. Although both BOP and DPK have the lowest triplet states chiefly of n pi* nature, the presence of other triplet states in the neighbourhood of the lowest triplet one is found to play some significant roles in determining the photophysical properties of DPK, specially in the non-polar solvent (MCH). All the photophysical properties including the polarization characteristics have been explored in both the molecules. Experimental observations are corroborated with necessary quantum chemical calculations.

Photodissociation of N-Arylmethylanilines: A Laser Flash Photolysis, Fluorescence, and Product Analysis Study(1)

Increased phenylation in the molecular series PhCH(2)NHPh (1), Ph(2)CHNHPh (2), and Ph(3)CNHPh(3) has two important consequences on the photophysical/photochemical behavior: (i) decrease in the fluorescence quantum yields (cyclohexane), Phi(f) = 0.115, 0.063, 0.001 (lambda(exc) = 254 nm) and 0.164, 0.089, 0.019 (lambda(exc) = 290 nm), respectively, and (ii) increase in the quantum yield (MeCN) of the photodissociation products PhCH(2)(*), Ph(2)CH(*), and Ph(3)C(*), Phi(radical) = 0.16, 0.25, 0.65 (lambda(exc) = 248 nm) and (not measured), 0.18, 0.29 (lambda(exc) = 308 nm), respectively. As the C-N bond progressively weakens in the series 1, 2, 3 (bond dissociation enthalpy: 52, 48, 39 kcal/mol, respectively), the C-N fission channel becomes obviously more favorable and competes effectively with fluorescence. The involved intermediates PhCH(2)(*), Ph(2)CH(*), Ph(3)C(*), and PhNH(*) were identified using laser flash photolysis (248 and 308 nm). Product analysis (lamp irradiation) gives as main products aniline and (i) 1,1-diphenylethane and o- and p-benzylaniline for 1, (ii) 1,1,2,2-tetraphenylethane for 2, (iii) Ph(3)CH and 9-Ph-fluorene for 3; all these compounds are formed from the above radicals through coupling or H-abstraction reactions.