A significant decrease in undercarboxylated osteocalcin (−0.945, −1.113 to −0.778) can be observed with the combination of vitamin K and D. Vitamin K combined with vitamin D significantly increased the total bone mineral density (BMD): the pooled effect size was 0.316. Method and findings: A comprehensive search on Web of Science, PubMed, Embase and the Cochrane Library (from 1950 to February 2020) and bibliographies of relevant articles was undertaken, with the meta-analysis of eight randomized controlled trials (RCTs) including a total of 971 subjects. The intense near-IR absorbance arises from the ion-pair charge transfer transition from 2- to 4,4'-bipyridinium.Background: Previous studies did not draw a consistent conclusion about the effects of vitamin K combined with vitamin D on human skeletal quality. The structure phase transition is responsible for these properties, as it leads to changes in the π-orbital overlap between the anion and cation in a mixed stack. Additionally, 1 exhibits irreversible mechanochromism, intense near-IR absorbance, and a dielectric anomaly. This is the first report of a green-colored crystal of bis(maleonitriledithiolato)nickelate(II) salt. Upon heating, 1 undergoes a reversible phase transition at around 340/320 K during the first heating/cooling cycle, resulting in rapid thermochromism with a color change from green (stable state) to red (metastable state) within a few seconds. These mixed stacks then combine to form a molecular solid through Coulomb and van der Waals interactions. In this study, we investigated a Ni-dithiolene dianion salt, 1,1'-diheptyl-4,4'-bipyridinium bis(maleonitriledithiolato)nickelate ( 1), and found that its cations and anions stack alternately to form a uniform mixed stack. A thermochromic or mechanochromic material can switch between at least two stable states in response to changes in temperature or static pressure/strain.
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