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The FT-Raman and UV-visible spectra of (12S)-1,4,7,10-tetraaxadicylclo[10,3,0]-pentadecane-3,11-dione and its derivatives were obtained and discussed. A dimolecular model, which considers hydrogen-bonded structures, proved that strong inter-and intramolecular hydrogen bonds are present in these compounds.

The fullerene-porphyrin interaction energies obtained for the four complexes are in the range from -16 to -18 kcal/mol. The change in the interaction energies ongoing from fullerene-porphyrin to fullerene-metalloporphyrin has not been significant because the increase of the electrostatic attractive forces has been offset by the increase of Pauli repulsive interactions.

Biodegradable flocculants are rarely used in waste activated sludge (WAS) fermentation. This study introduces an alginate-based biodegradable flocculant (ABF) to enhance both the dewatering and degradation of WAS during its fermentation. Alginate was identified in structural extracellular polymeric substances (St-EPS) of WAS, with alginate-producing bacteria comprising ∼4.2% of the total bacterial population in WAS. Owing to its larger floc size, higher contact angle, and lower free energy resulting from the Lewis acid-base interaction, the addition of the prepared ABF with a network structure significantly improved the dewaterability of WAS and reduced capillary suction time (CST) by 72%. The utilization of ABF by an enriched alginate-degrading consortium (ADC) resulted in a 35.5% increase in the WAS methane yield owing to its higher hydrolytic activity on both ABF and St-EPS. Additionally, after a 30 day fermentation, CST decreased by 62% owing to the enhanced degradation of St-EPS (74.4%) and lower viscosity in the WAS + ABF + ADC group. The genus Bacteroides , comprising 12% of ADC, used alginate lyase (EC 4.2.2.3) and pectate lyase (EC 4.2.2.2 and EC 4.2.2.9) to degrade alginate and polygalacturonate in St-EPS, respectively. Therefore, this study introduces a new flocculant and elucidates its dual roles in enhancing both the dewaterability and degradability of WAS. These advancements improve WAS fermentation, resulting in higher methane production and lower CSTs.

The kinematic time and maximum spreading time for the impact of nanodroplets of different types of fluids on solid surfaces with different wettability are investigated. It shows that the capillary regime still exits for the nanodroplet impact, even if viscous dissipation increases significantly when the droplet size reduces to the nanoscale. By taking into account the influence of liquid types and surface wettability, we first obtain scaling laws of the maximum spreading time for the capillary and viscous regimes. We further propose a universal scaling law by interpolating the scaling laws in the two asymptotic regimes. The universal scaling law is in excellent agreement with molecular dynamics simulations for various liquids and surface wettability.

Noncovalent interactions between aromatic compounds and fullerenes have received considerable attention in various fields of science and technology. Employing benzene (C6H6) and C60 fullerene as model molecules, we theoretically explored in the present study the nature of this kind of noncovalent interaction. Our results clearly show that the π···π stacking configurations of the complex C6H6···C60 are more strongly bound than in the C-H···π analogues, and the C-H···π interactions in the C-H···π configurations of C6H6···C60 are not of the hydrogen bonds. According to symmetry adapted perturbation theory analyses, all of the configurations of C6H6···C60 are dominated by dispersion forces. The percentage of the dispersion components in the overall attractive interactions for the π···π stacking configurations is smaller than the percentage of the dispersion components in the overall attractive interactions for the C-H···π configurations, whereas the percentage of the electrostatic terms in the overall attractive interactions for the π···π stacking configurations is larger than the percentage of the electrostatic terms in the overall attractive interactions for the C-H···π configurations. This is distinctly different from the case of the benzene dimer.

The π···π stacking interactions between homogeneous dimers of C(6)F(x)I((6-x)) (x = 0, 1, 2, 3, 4, and 5) have been investigated in detail using the state-of-the-art quantum chemistry methods. Computations clearly show that the π···π stacking interaction between the homogeneous dimer of C(6)F(x)I((6-x)) is of the dispersion type interaction. At the same time, it is interesting to find that, for the π···π stacking interactions between homogeneous dimers of C(6)F(x)I((6-x)), the M05-2X/def2-TZVPP computations give almost the same results as the CCSD(T)/SDD** computations. In the crystal growth and design, the formation of the π···π stacking interactions between homogeneous dimers of C(6)F(x)I((6-x)) is always accompanied by the formation of the halogen bonds. Hence, competition and cooperation of the π···π stacking interaction and the halogen bond have also been studied theoretically by using C(6)F(x)I((6-x)) and pyridine as coformers. At the M05-2X/def2-TZVPP theory level, it is found that the π···π stacking interactions in C(6)F(5)I···C(6)F(5)I and C(6)F(4)I(2)···C(6)F(4)I(2) are weaker than the corresponding halogen bonds in C(6)F(5)I···NC(5)H(5) and C(6)F(4)I(2)···NC(5)H(5), and the π···π stacking interactions in C(6)FI(5)···C(6)FI(5) and C(6)I(6)···C(6)I(6) are stronger than the corresponding halogen bonds in C(6)FI(5)···NC(5)H(5) and C(6)I(6)···NC(5)H(5), while the strengths of the π···π stacking interactions in C(6)F(3)I(3)···C(6)F(3)I(3) and C(6)F(2)I(4)···C(6)F(2)I(4) are similar to the corresponding halogen bonds in C(6)F(3)I(3)···NC(5)H(5) and C(6)F(2)I(4)···NC(5)H(5). However, when the π···π stacking interaction and the halogen bond coexist, we find that the formation of the halogen bond will lead to the π···π stacking interaction much stronger, and vice versa.

The reactions of H(2)COO with HO(2) and the HO(2)···H(2)O complex are studied by employing the high-level quantum chemical calculations with B3LYP and CCSD(T) theoretical methods, the conventional transition-state theory (CTST), and the Rice-Ramsperger-Kassel-Marcus (RRKM) with Eckart tunneling correction. The calculated results show that the proton transfer plus the addition reaction channel (TS1A) is preferable for the reaction of H(2)COO with HO(2) because the barriers are -10.8 and 1.6 kcal/mol relative to the free reactants and the prereactive complex, respectively, at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(d,p) level of theory. Furthermore, the rate constant via TS1A (2.23 × 10(-10) cm(3) molecule(-1) s(-1)) combined with the concentrations of the species in the atmosphere demonstrates that the HO(2) radical would be the dominant sink of H(2)COO in some areas, where the concentration of water is less than 10(17) molecules cm(-3). In addition, although the single water molecule would lower the activated barrier of TS1A from 1.0 to 0.1 kcal/mol with respect to the respective complexes, the rate constant is lower than that of the reaction of HO(2) with H(2)COO.

The reactions of H2SO4 with the OH radical without water and with water are investigated employing the quantum chemical calculations at the B3LYP/6-311+G(2df,2p) and MP2/aug-cc-pv(T+d)z levels of theory, respectively. The calculated results show that the reaction of H2SO4 with OH and H2O is a very complex mechanism because of the formation of the prereactive complex prior to the transition state and product. There are two prereactive complexes with stabilization energies being -20.28 and -20.67 kcal/mol, respectively. In addition, the single water can lower the energy barriers of the hydrogen abstraction and the proton transfer to 7.51 and 6.37 kcal/mol, respectively from 13.79 and 8.82 kcal/mol with respect to the corresponding prereactive complex. The computed rate constants indicate that the water-assisted reaction of sulfuric acid with OH radical is of greater importance than the reaction of the naked sulfuric acid with the OH radical because the rate constant of the water-assisted process is about 10(3) faster than that of the reaction sulfuric acid with OH. Therefore, the conclusion is obtained that the water-assisted process plays an important role in the sink for the gaseous sulfuric acid in the clean area.

FT-IR, FT-Raman and electronic absorption spectroscopies were utilized in conjunction with density functional theory (DFT) calculations to investigate the ground and excited states of self-assembled dinuclear dimeric helicates (ZnL)2 and (NiL)2 [L = bis(2,4-dimethyldipyrrin-3-yl)methane]. These studies afford a detailed description of the ground-state geometric and electronic structures of (ZnL)2 and (NiL)2 and provide a comparison with similar geometrical metal-porphyrins. The results demonstrate that enlarging the basis set used in the DFT calculations results in an obvious alteration of the calculated bond lengths but negligible alteration of the calculated bond angles. The predicted spectra are in good agreement with the experimental ones with the deviations generally less than 30 cm(-1). In comparison with vibrational spectra of metal-porphyrins, the breathing vibration of the pyrrole ring is shifted by over 100 cm(-1) toward higher wavenumber due to local conjugation of molecular geometry. Time-dependent density functional theory (TD-DFT) provides a good description of the excitation energy. Because of the break in symmetry, the absorption band (corresponding to the Q-band of porphyrin) of (ZnL)2 and (NiL)2 is no longer weak. Local conjugation makes the absorption wavelength of (NiL)2 and (ZnL)2 shift to the blue compared with those of NiP and ZnP.