Concomitance of octamolybdate isomers in metastable crystal structures isolated using homoleptic CoII/CoIII complexes as structure-directing templates

Exploiting the kinetic domain provided by hydrothermal conditions, it was possible to isolate three transient metastable crystal structures, each bearing concomitant pairs of octamolybdate isomers, namely, α – β , γ – β or β cs – β gp stabilized by distinctive homoleptic [Co(bpy)3]n+ (bpy   = 2,2 ′ -bipyridine; n   = 2 or 3) cations generated in situ: [Co(bpy)3]4[( α -Mo8O26)( β -Mo8O26)] · 5H2O (1), [NH4][Co(bpy)3][( γ -Mo8O26)0.5( β -Mo8O26)0.5] · 4H2O (2) and [Co(bpy)3]2[( β cs-Mo8O26)0.5( β gp-Mo8O26)] · 12H2O (3). Solid 1 with the space group P21/n and unit-cell parameters a   = 22.160   (6), b   = 14.209   (3), c   = 24.641   (4)   Å , β   = 99.10   (2) ° and V   = 7661   (3)   Å 3 resulted in the same crystal structure as that synthesized previously under different conditions by Sun et al. [J. Mol. Struct. (2005), 741, 149 – 153]. Factors directing the reaction, such as product composition and phase stability, were monitored by analysis of the PXRD patterns of the bulk solids obtained under different experimental conditions. The relative proportions of the mixed phases 1 – 3 or their stabilization are highly dependent on the initial Co:Mo molar ratio and the reaction temperature. In particular, an increase in temperature induces the transformation of 1 – 3 into more thermodynamically stable phases formed by one-dimensional coordination polymers [Co(bpy)2( β -Mo8O26)0.5]n (4) and [(MoO3)(bpy)]n (5). The crystal stru...

Source: Acta Crystallographica Section B - January 22, 2021 Category: Chemistry Authors: Atencio, R. Brice ñ o, A. Bruno-Colmenarez, J. Silva, P. Rodr í guez, L. Sosa, E. Limones, E. Pacheco, Y. C á ceres, J. Vielma, J. Tags: octamolybdate crystal structure metastability cobalt isomer structure-directing template research papers Source Type: research