RESUMO
As a novel type of macrocycles with attractive planar chirality, pillar[5]arenes have gained increasing research interest over the past decades, enabling their widespread applications in diverse fields such as porous materials, molecular machines, and chiral luminescence materials. However, the catalytic methodology towards the enantioselective synthesis of planar chiral pillar[5]arenes remains elusive. Here we report a novel method for the enantioselective synthesis of planar chiral pillar[5]arenes via asymmetric Sonogashira coupling, giving access to a wide range of highly functionalized planar chiral pillar[5]arenes, including both homo- and hetero-rimmed ones, with excellent enantioselectivities. Attractively, the resultant planar chiral pillar[5]arenes show great potential for widespread use in many areas such as chiral luminescent materials. This work not only enables the successful synthesis of planar chiral pillar[5]arenes with abundant structural and functional diversity as key building blocks for practical applications but also enriches the asymmetric cross-coupling methodologies in organic synthetic chemistry.
RESUMO
We propose the newly synthesizedß-BaNi3(VO4)2(OH)2(space group:R3â¾m) as a candidate for the spin-1 kagome Heisenberg antiferromagnet (KHA). The compound features a uniform kagome lattice of Ni2+(S= 1) ions with a large interlayer distance. High-field measurements at low temperatures reveal a susceptibility local minimum at â¼9 T, resembling a 1/3 magnetization plateau as predicted by the pureS= 1 KHA model. Below â¼6 K, approximately 1% of the spins exhibit spin-glass order, which may be attributed to the nanocrystalline grain size of â¼50 nm. Despite the antiferromagnetic exchange coupling strength of â¼7 K, the majority of spins remain disordered down to â¼0.1 K as indicated by the observed power-law behaviors in magnetic specific heatCmâT1.4. Our results demonstrate that the low-energy magnetic excitations inß-BaNi3(VO4)2(OH)2are gapless, which contradicts the current theoretical expectations of the ideal model.
RESUMO
There has been a call for increased attention to experiences of sociocultural contexts and their role in mental health and help-seeking among specific subgroups of Asian Americans (Leong, Park, & Kalibatseva, 2013). In particular, as suggested by the integrative contextual framework of minority youth development (García Coll & Marks, 2012), racial minority adolescents and emerging adults develop identity and psychological well-being through their experiences within multiple contexts. Guided by this perspective, the present study examined the role of specific developmental and contextual factors (e.g., acculturation-based intergenerational family conflict and ethnic identity) on depressive and anxiety symptoms and help-seeking attitudes among Chinese American college students. One-hundred and 73 Chinese American college students (132 women and 36 men) from various geographic regions in the U.S. completed a series of questionnaires administered online, assessing acculturation-based intergenerational family conflict, ethnic identity, depressive and anxiety symptoms, and help-seeking attitudes. The findings indicated that the seriousness of acculturation-based intergenerational family conflict and the commitment dimension of ethnic identity were associated with symptoms of depression and anxiety. Additionally, the exploration dimension of ethnic identity was associated with less favorable attitudes toward seeking help from mental health professionals. There was no association between acculturation-based intergenerational family conflict and help-seeking attitudes. The findings underscore the importance of developing culturally informed interventions that attend to the intensity of family conflict and one's sense of connection to ethnic community in the college context. (PsycInfo Database Record (c) 2021 APA, all rights reserved).