ABSTRACT
A novel calcium carbonate cement system that mimics the naturally occurring mineralization process of carbon dioxide to biogenic or geologic calcium carbonate deposits was developed utilizing carbon dioxide-containing flue gas and high-calcium industrial solid waste as raw materials. The calcium carbonate cement reaction is based on the polymorphic transformation from metastable vaterite to aragonite and can achieve >40 MPa compressive strength. Due to its unique properties, the calcium carbonate cement is well suited for building materials applications with controlled factory manufacturing processes that can take advantage of its rapid curing at elevated temperatures and lower density for competitive advantages. Examples of suitable applications are lightweight fiber cement board and aerated concrete. The new cement system described is an environmentally sustainable alternative cement that can be carbon negative, meaning more carbon dioxide is captured during its manufacture than is emitted.
ABSTRACT
In the chromophore-quencher complex fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (Aqphen is 12,17-dihydronaphtho[2,3-h]dipyrido[3,2-a:2',3'-c]-phenazine-12,17-dione; py-PTZ is 10-(4-picolyl)phenothiazine), Aqphen is a dppz derivative, containing a pendant quinone acceptor at the terminus of a rigid ligand framework. This introduces a third, low-lying, ligand-based pi acceptor level localized largely on the quinone fragment. Laser flash excitation of fac-[Re(Aqphen)(CO)(3)(py-PTZ)](+) (354.7 nm; in 1,2-dichloroethane) results in the appearance of a relatively long-lived transient that decays with tau(298K) = 300 ns (k = 3.3 x 10(6) s(-)(1)). Application of transient absorption, time-resolved resonance Raman, and time-resolved infrared spectroscopies proves that this transient is the redox-separated state fac-[Re(I)(Aqphen(*)(-)())(CO)(3)(py-PTZ(*)(+)())](+) in which the excited electron is localized largely on the quinone portion of the Aqphen ligand.
ABSTRACT
The polymer poly[4-(2-aminoethyl)styrene], prepared by living anionic polymerization, has been derivatized by amide coupling to [Ru(II)(vbpy)(2)(4-CO(2)H-4'-CH(3)bpy)](2+) (vbpy is 4-vinyl-4'-methyl-2,2'-bipyridine; 4-CO(2)H-4'-CH(3)bpy is 4-methyl-2,2'-bipyridine-4'-carboxylic acid). The resulting "macromer" can be electropolymerized on a variety of electrode materials by reductive electropolymerization. Compared to similar films of poly[Ru(II)(vbpy)(3)](PF(6))(2): (1) the macromeric films are considerably rougher, apparently having open, local microporous structures; (2) they undergo comparable rates of intrafilm charge transfer; and (3) they have shortened metal-to-ligand charge transfer (MLCT) excited state lifetimes, apparently due to quenching by film-based trap sites. Stable films of a mixed polymer have also been prepared by sequential addition of [Ru(II)(bpy)(2)(4-CO(2)H-4'-CH(3)bpy)](2+) and then the vbpy derivative.
ABSTRACT
[Os(tpy)(bpy)(NH(3))](PF(6))(2) (1) was oxidized electrochemically in the presence of a series of amines in aqueous solutions buffered to pH 7. With secondary aliphatic amines, electrolysis gave [Os(tpy)(bpy)(NNR(2))](PF(6))(3) (3); number of electrons n = 4.6-5.0. 3 was reduced to [Os(tpy)(bpy)(NNR(2))](PF(6))(2) (2) in aqueous and nonaqueous solutions with n = 1.0. The structures of 2 were determined by X-ray crystallography for NR(2) = diethylamide (2a) and morpholide (2c) and were found to exhibit bent hydrazido(2-) coordination (Os-N-N = 137 degrees ). The salts crystallized in the triclinic system, space group P&onemacr;. For 2a, a = 9.004(1) Å, b = 9.796(1) Å, c = 20.710(2) Å, alpha = 88.78(2) degrees, beta = 85.43(2) degrees, gamma = 86.22(2) degrees, and Z = 2. For 2c, a = 9.632(8) Å, b = 21.229(9) Å, c = 9.039(5) Å, alpha = 97.41(4) degrees, beta = 94.28(5) degrees, gamma = 85.07(5) degrees, and Z = 2. Solutions of 2 were protonated in strongly acidic media to give hydrazido(1-) complexes. The pK(a) of the protonated form of 2a is 0.90 +/- 0.01. Reduction of 2 in aqueous solutions of pH <1 gave 1 and NH(2)R(2)(+) with n = 4.0. At higher pH, there is evidence for an Os(II) hydrazine intermediate. Oxidation of 3 by one electron afforded transiently stable species which decomposed to give [Os(tpy)(bpy)(NCCH(3))](3+) in acetonitrile solution. Pseudo-first-order rate constants of 8.1 +/- 0.9 s(-)(1) and 0.200 +/-.005 s(-)(1) were estimated by cyclic voltammetry on solutions of 2a and 2b(NR(2) = piperidide), respectively. Oxidation of 1 at pH 7, in the presence of primary aliphatic amines or ammonia, occurred with n = 5.9-6.2, and generated [Os(II)(tpy)(bpy)(N(2))](PF(6))(2) (4).
