Exploring the relationship between older adults' online health information seeking, negative emotions and prevention behaviors in the pandemic context: a two-wave longitudinal study.

Introduction: During the COVID-19 pandemic, older adults were facing more mental health issues that may cause complex impacts on pandemic prevention, and turning to the internet for health information is a double-edged sword for them. This study aimed to investigate the reciprocal relationship between negative emotions and prevention behaviors in older adults, as well as the direct and moderating effects of online health information seeking (OHIS) on negative emotions and prevention behaviors. Methods: Based on the common-sense model of self-regulation (CSM) and a sample of more than 20,000 participants from the Survey of Health, Aging and Retirement in Europe (SHARE), this study first used an autoregressive cross-lagged panel model (CLPM) to analyze the longitudinal effect of negative emotions on prevention behaviors. Second, the study used ordinary least squares (OLS) regression to explore the influence of OHIS usage frequency changes on negative emotions and prevention behaviors. Third, the study used multigroup analysis to examine the moderating effect of OHIS usage frequency changes on the CLPM. Results: The findings indicate a significant longitudinal association where initial negative emotions predicted later prevention behaviors (ß = 0.038, p < 0.001), and increased OHIS frequency was linked to positive changes in prevention behavior (ß = 0.109, p < 0.001). Multigroup analysis revealed that the connection between negative emotions or increased negative emotions and prevention behaviors remained significant for those with no change or an increase in OHIS frequency but not for those with a decrease. Conclusion: This study suggested that negative emotions may drive older adults to engage more in prevention behaviors and that OHIS can augment this effect. These results underscore the importance of addressing mental health and providing reliable online health information to support older adults in managing infectious disease risks.

Influence of Metal Identity and Complex Nuclearity in Kumada Cross-Coupling Polymerizations with a Pyridine Diimine-Based Ligand Scaffold.

Cross-coupling polymerizations have fundamentally changed the field of conjugated polymers (CPs) by expanding the scope of accessible materials. Despite the prevalence of cross-coupling in CP synthesis, almost all polymerizations rely on mononuclear Ni or Pd catalysts. Here, we report a systematic exploration of mono- and dinuclear Fe and Ni precatalysts with a pyridine diimine ligand scaffold for Kumada cross-coupling polymerization of a donor thiophene and an acceptor benzotriazole monomers. We observe that variation of the metal identity from Ni to Fe produces contrasting polymerization mechanisms, while complex nuclearity has a minimal impact on reactivity. Specifically, Fe complexes appear to catalyze step-growth Kumada polymerizations and can readily access both Csp2-Csp3 and Csp2-Csp2 cross-couplings, while Ni complexes catalyze chain-growth polymerizations and predominantly Csp2-Csp2 cross-couplings. Thus, our work sheds light on important design parameters for transition metal complexes used in cross-coupling polymerizations, demonstrates the viability of iron catalysis in Kumada polymerization, and opens the door to novel polymer compositions.

C-C σ-Bond Oxidative Addition and Hydrofunctionalization by a Macrocycle-Supported Diiron Complex.

This report describes the first examples of unassisted C(sp)-C(sp2) and C(sp)-C(sp3) bond oxidative addition reactions to give thermodynamically favorable products. Treatment of a diiron complex supported by a geometrically and electronically flexible macrocyclic ligand, (3PDI2)Fe2(µ-N2)(PPh3)2 ([Fe2N2]0), with stoichiometric amounts of various 4,4'-disubstituted diphenylacetylenes (ArX-C≡C-ArX; X = OMe, H, F, CF3) yielded C(sp)-C(sp2) bond oxidative addition products. When Ph-C≡C-R substrates were used as substrates (R = Me, Et, iPr, tBu), products of either C(sp)-C(sp2) or C(sp)-C(sp3) bond activation were obtained, with the less sterically encumbering alkynes exclusively undergoing C(sp)-C(sp3) bond activation. Treatment of the C-C activation species with either H2 or HBpin was found to form products of C-C σ-bond hydrofunctionalization. In both the hydrogenation and hydroboration schemes, the diiron species was observed to return to [Fe2N2]0, thereby completing synthetic cycles for C-C σ-bond functionalization.

Tuning metal-metal interactions for cooperative small molecule activation.

Cluster complexes have attracted interest for decades due to their promise of drawing analogies to metallic surfaces and metalloenzyme active sites, but only recently have chemists started to develop ligand scaffolds that are specifically designed to support multinuclear transition metal cores. Such ligands not only hold multiple metal centers in close proximity but also allow for fine-tuning of their electronic structures and surrounding steric environments. This Feature Article highlights ligand designs that allow for cooperative small molecule activation at cluster complexes, with a particular focus on complexes that contain metal-metal bonds. Two useful ligand-design elements have emerged from this work: a degree of geometric flexibility, which allows for novel small molecule activation modes, and the use of redox-active ligands to provide electronic flexibility to the cluster core. The authors have incorporated these factors into a unique class of dinucleating macrocycles (nPDI2). Redox-active fragments in nPDI2 mimic the weak-overlap covalent bonding that is characteristic of M-M interactions, and aliphatic linkers in the ligand backbone provide geometric flexibility, allowing for interconversion between a range of geometries as the dinuclear core responds to the requirements of various small molecule substrates. The union of these design elements appears to be a powerful combination for analogizing critical aspects of heterogeneous and metalloenzyme catalysts.

N-H Bond Formation at a Diiron Bridging Nitride.

Despite their connection to ammonia synthesis, little is known about the ability of iron-bound, bridging nitrides to form N-H bonds. Herein we report a linear diiron bridging nitride complex supported by a redox-active macrocycle. The unique ability of the ligand scaffold to adapt to the geometric preference of the bridging species was found to facilitate the formation of N-H bonds via proton-coupled electron transfer to generate a µ-amide product. The structurally analogous µ-silyl- and µ-borylamide complexes were shown to form from the net insertion of the nitride into the E-H bonds (E=B, Si). Protonation of the parent bridging amide produced ammonia in high yield, and treatment of the nitride with PhSH was found to liberate NH3 in high yield through a reaction that engages the redox-activity of the ligand during PCET.

Mimicking the Constrained Geometry of a Nitrogen-Fixation Intermediate.

Both biological and industrial nitrogen reduction catalysts activate N2 at multinuclear binding sites with constrained Fe-Fe distances. This contrasts with molecular diiron systems, which routinely form linear N2 bridges to minimize steric interactions. Model compounds that capture the salient geometric features of N2 binding by the nitrogenase enzymes and Mittasch catalysts would contribute to understanding their high N2-reduction activity. It is shown in the present study that use of a geometrically flexible, dinucleating macrocycle allows for the formation of a bridging N2 ligand with an unusual Fe-CtN2-Fe angle of 150° (CtN2 = centroid of N2), a geometry that approximates the α-N2 binding mode on Fe(111) surfaces that precedes N2 bond cleavage. The cavity size of the macrocycle prevents the formation of a linear Fe-N2-Fe unit and leads to orbital interactions that are distinct from those available to the linear configuration.