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Understanding how poly(carboxylate)s of chemical admixtures interact with calcium ions in cement pore solutions in the presence of silica fume is fundamental to developing better chemical admixtures for concrete production. In this work, the intermolecular interactions of calcium ions with a poly(carboxylate) superplasticizer type of chemical admixture was investigated via classical all-atom molecular dynamics (MD) simulations and Density Functional Theory (DFT) calculation methods in the presence of silica fume. The classical all-atom MD simulation and DFT calculation results indicate that calcium ions are interacting with oxygen atoms of the carboxylate group of PCE. The better interaction energy could mean an improved adsorption of the PCE segment with calcium ions. In this regard, it can be noted that the ester-based PCE segment could have a better adsorption onto calcium ions in comparison with the ether-based PCE segment. Moreover, the presence of silicon dioxide could improve the adsorption of the PCE segment onto calcium ions. [ABSTRACT FROM AUTHOR]

Complexes consisting of earth-abundant main group metals such as silicon with polypyridine ligands are of interest for a variety of optical and electronic applications including as electrochromic colorants. Previous spectroelectrochemical studies with tris(2,2′-bipyridyl)silicon(IV) hexafluorophosphate, [Si(bpy)3](PF6)4, demonstrated an ability to control the color saturation of the potential electrochromic dye, with the intensity of the dye's green color increasing as the charge state sequentially reduces from 4+ to 1+. In this study, the synthesis of bis(4′-(4-tolyl)-2,2′:6′,2″-terpyridine)silicon(IV) hexafluorophosphate, [Si(ttpy)2](PF6)4, is reported along with electrochemical and spectroelectrochemical analyses. Computational modeling (density functional theory) is used to further elucidate the electrochromic properties of previously reported Si(bpy)3n+ species and the new Si(ttpy)2n+ species. While the homoleptic tris(bidentate)silicon(IV) complexes are attractive as electrochromic dyes for tunable color saturation, the bis(tridentate)silicon(IV) complexes are attractive as polychromatic electrochromic dyes. [ABSTRACT FROM AUTHOR]

Geometry optimizations of monomers were carried out with the use of Becke's three-parameter hybrid method with Lee, Yang, and Parr (B3LYP) gradient-corrected correlation functional and the standard 6-31G(d) basis set. UV-vis spectra of different naphthalene-POPOP complexes using ZINDO/S method were calculated. In these complexes, poly(methyl methacrylate) effect on chromophores was neglected and chromophores were staked. Analyzing available experimental data and obtained theoretical results, the most probable complex structure is determined. Molecular model of POPOP and naphthalene dimer corresponds to this structure. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]