Palladium-anchored donor-flexible pyridylidene amide (PYA) electrocatalysts for CO2 reduction.

The conversion of CO2 into CO as a substitute for processing fossil fuels to produce hydrocarbons is a sustainable, carbon neutral energy technology. However, the electrochemical reduction of CO2 into a synthesis gas (CO and H2) at a commercial scale requires an efficient electrocatalyst. In this perspective, a series of six new palladium complexes with the general formula [Pd(L)(Y)]Y, where L is a donor-flexible PYA, N2,N6-bis(1-ethylpyridin-4(1H)-ylidene)pyridine-2,6-dicarboxamide, N2,N6-bis(1-butylpyridin-4(1H)-ylidene)pyridine-2,6-dicarboxamide, or N2,N6-bis(1-benzylpyridin-4(1H)-ylidene)pyridine-2,6-dicarboxamide, and Y = OAc or Cl-, were utilized as active electrocatalysts for the conversion of CO2 into a synthesis gas. These palladium(ii) pincer complexes were synthesized from their respective H-PYA proligands using 1,8-diazobicyclo[5.4.0]undec-7-ene (DBU) or sodium acetate as a base. All the compounds were successfully characterized by various physical methods of analysis, such as proton and carbon NMR, FTIR, CHN, and single-crystal XRD. The redox chemistry of palladium complexes toward carbon dioxide activation suggested an evident CO2 interaction with each Pd(ii) catalyst. [Pd(N2,N6-bis(1-ethylpyridin-4(1H)-ylidene)pyridine-2,6-dicarboxamide)(Cl)]Cl showed the best electrocatalytic activity for CO2 reduction into a synthesis gas under the acidic condition of trifluoracetic acid (TFA) with a minimum overpotential of 0.40 V, a maximum turnover frequency (TOF) of 101 s-1, and 58% FE of CO. This pincer scaffold could be stereochemically tuned with the exploration of earth abundant first row transition metals for further improvements in the CO2 reduction chemistry.

Prevalence of HIV among pregnant women in three HIV-affected districts in Sindh, Pakistan.

OBJECTIVE: To conduct a community-based cross-sectional survey to determine the prevalence of human immunodeficiency virus (HIV) among pregnant women in taluka Ratodero, Larkana, and two adjacent talukas: Sajawal, district Kambar Shahdadkot and Garhi Yasin, district Shikarpur. METHODS: The study was conducted among pregnant women in the three talukas of rural Sindh: Ratodero, Garhi Yasin, and Sajawal, from October 16, 2020 - December 23, 2020. A total of 1,157 pregnant women were interviewed at their homes and tested using the AlereTM HIV Combo rapid finger prick test. The study captured women's sociodemographic, economic, and health characteristics, including age, education, employment, number of children, home or hospital delivery, antenatal care use, antenatal trimester, history of blood transfusion, and HIV test result. Descriptive statistics were calculated: percentages for categorical variables and mean ± standard deviation (SD) for continuous variables. RESULTS: It was found that 0.35% (4/1,157) of women were HIV-positive, of which 3 were in Ratodero, Larkana, and 1 was in Garhi Yasin, Shikarpur. The average age of women was 28.7 ± 4.0 years. Most of the women (n=1067; 92.2%) did not attend a school, and 99.0% (n=1145) had never had a formal job. The average gestational age was 7.6 (±2.2) months. More than three-quarters of the women participating in the study (n=894; 77.3%) were not registered with a formal healthcare facility for antenatal care. CONCLUSIONS: Considering several HIV sub-epidemics in Larkana in the past decade, HIV infection among pregnant women has remained low in Larkana and adjacent districts.

Reaction of a Molybdenum Bis(dinitrogen) Complex with Carbon Dioxide: A Combined Experimental and Computational Investigation.

Refluxing Mo(CO)6 in the presence of the phosphine-functionalized α-diimine ligand Ph2PPrDI allowed for substitution and formation of the dicarbonyl complex, (Ph2PPrDI)Mo(CO)2. Oxidation with I2 followed by heating resulted in further CO dissociation and isolation of the corresponding diiodide complex, (Ph2PPrDI)MoI2. Reduction of this complex under a N2 atmosphere afforded the corresponding bis(dinitrogen) complex, (Ph2PPrDI)Mo(N2)2. The solid-state structures of all three compounds were found to feature a tetradentate chelate and cis-monodentate ligands. Notably, the addition of CO2 to (Ph2PPrDI)Mo(N2)2 is proposed to result in head-to-tail CO2 coupling to generate the corresponding metallacycle and ultimately a mixture of (Ph2PPrDI)Mo(CO)2 and the bis(oxo) dimer, [(κ3-Ph2PPrDI)Mo(O)(µ-O)]2. Computational studies have been performed to gain insight into the reaction and evaluate the importance of cis-coordination sites for selective head-to-tail CO2 reductive coupling, CO deinsertion, disproportionation, and stepwise CO2 deinsertion.