ABSTRACT
The catalytic efficacy of the monobipyridyl (η6-para-Cymene)Ru(II) half-metallocene, [(p-Cym)Ru(bpy)Cl]+ was evaluated in both mixed homogeneous (dye + catalyst) and heterogeneous hybrid systems (dye/TiO2/Catalyst) for photochemical CO2 reduction. A series of homogeneous photolysis experiments revealed that the (p-Cym)Ru(II) catalyst engages in two competitive routes for CO2 reduction (CO2 to formate conversion via RuII-hydride vs CO2 to CO conversion through a RuII-COOH intermediate). The conversion activity and product selectivity were notably impacted by the pKa value and the concentration of the proton source added. When a more acidic TEOA additive was introduced, the half-metallocene Ru(II) catalyst leaned toward producing formate through the RuII-H mechanism, with a formate selectivity of 86%. On the other hand, in homogeneous catalysis with TFE additive, the CO2-to-formate conversion through RuII-H was less effective, yielding a more efficient CO2-to-CO conversion with a selectivity of >80% (TONformate of 140 and TONCO of 626 over 48 h). The preference between the two pathways was elucidated through an electrochemical mechanistic study, monitoring the fate of the metal-hydride intermediate. Compared to the homogeneous system, the TiO2-heterogenized (p-Cym)Ru(II) catalyst demonstrated enhanced and enduring performance, attaining TONs of 1000 for CO2-to-CO and 665 for CO2-to-formate.
ABSTRACT
We developed an effective binding free energy prediction protocol which incorporates quantum mechanical/molecular mechanical (QM/MM) calculations to substitute the specified atomic charges of force fields with quantum-mechanically recalculated ones at a proposed pose using a mining minima approach with the VeraChem mining minima engine. We tested this protocol using seven well-known targets with 147 different ligands and compared it with classical mining minima and the most popular binding free energy (BFE) methods using different metrics. Our new protocol, dubbed Qcharge-VM2, yielded an overall Pearson correlation of 0.86, which was better than all the methods examined. Qcharge-VM2 performed significantly better than implicit solvent-based methods, such as MM-GBSA and MM-PBSA, but not as good as explicit water-based free energy perturbation methods, such as FEP+, in terms of root-mean-square error, RMSE (1.75 kcal/mol) and mean unsigned error, MUE (1.39 kcal/mol) on a limited set of targets. However, our protocol is substantially less computationally demanding compared with FEP+. The combined accuracy and efficiency of our method can be valuable in drug discovery campaigns.
Subject(s)
Proteins , Ligands , Proteins/chemistry , Entropy , Protein Binding , Solvents/chemistry , ThermodynamicsABSTRACT
Interaction of the alkali metals (AMs) like lithium (Li), sodium (Na), and potassium (K) with defective and non-defective (8,0) C3N nanotubes (C3NNT) have been investigated using the first-principles study. In addition to structural properties, we have also studied the electronic properties, charge transfer, and work function of the AM-C3NNT complexes. AMs are adsorbed on hollow sites, regardless of the initial positions. Upon the adsorption of AMs, the structures exhibit semiconducting behavior. Furthermore, interaction of Li atom can be explained by Dewar model, whereas for the other atoms there are different explanations. For all metal adsorbates, the direction of the charge transfer is from adsorbate to adsorbent, because of their high surface reactivity. The results showed that the nanotube with carbon vacancy is the most favorite adsorbent. Our findings also indicated that the enhancement in absolute adsorption energy is in order of Li > K > Na. It is noteworthy that clustering of AM atoms on the nanotubes with and without defects is not expected. It is worthy that C3NNT is a better adsorbent for AM atoms than CNT, graphene, C60, and B80.
