Cationic polymers show promise for the in vitro and in vivo delivery of macromolecular therapeutics. Known cationic polymers, e.g., poly(L)lysine (PLL) and polyethylenimine (PEI), have been employed in native and modified forms for the delivery of plasmid DNA (pDNA) and reveal varying levels of toxicity. Here, we report the preparation of a new class of cationic polymers that are specifically designed to deliver macromolecular therapeutics. Linear, cationic, beta-cyclodextrin (beta-CD)-containing polymers (CD-polymers) are synthesized by copolymerizing difunctionalized beta-CD monomers (AA) with other difunctionalized comonomers (BB) such that an AABBAABB product is formed. The beta-CD polymers are able to bind approximately 5 kbp pDNA above polymer to DNA (+/-) charge ratios of 1.5, compact the bound pDNA into particles of approximately 100-150 nm in size at charge ratios above 5+/-, and transfect cultured cells at charge ratios above 10+/-. In vitro transfections with the new beta-CD-polymers are comparable to the best results obtained in our hands with PEI and Lipofectamine. Some cell line-dependent toxicities are observed for serum-free transfections; however, no toxicity is revealed at charge ratios as high as 70+/- in transfections conducted in 10% serum. Single IV and IP doses as high as 200 mg/kg in mice showed no mortalities.

Cationic platinum(II) complexes [( t bpy)Pt(Ph)(L)]+ [ t bpy =4,4′-di-tert-butyl-2,2′-bipyridyl; L = THF, NC5F5, or NCMe] catalyze the hydrophenylation of ethylene to generate ethylbenzene and isomers of diethylbenzene. Using ethylene as the limiting reagent, an 89% yield of alkyl arene products is achieved after 4 h at 120 °C. Catalyst efficiency for ethylene hydrophenylation is diminished only slightly under aerobic conditions. Mechanistic studies support a reaction pathway that involves ethylene coordination to Pt(II), insertion of ethylene into the Pt–phenyl bond, and subsequent metal-mediated benzene C–H activation. Studies of stoichiometric benzene (C6H6 or C6D6) C–H/C–D activation by [( t bpy)Pt(Ph-d n )(THF)]+ (n = 0 or 5) indicate a k H/k D = 1.4(1), while comparative rates of ethylene hydrophenylation using C6H6 and C6D6 reveal k H/k D = 1.8(4) for the overall catalytic reaction. DFT calculations suggest that the transition state for benzene C–H activation is the highest energy species along the catalytic cycle. In CD2Cl2, [( t bpy)Pt(Ph)(THF)][BAr′4] [Ar′ = 3,5-bis(trifluoromethyl)phenyl] reacts with ethylene to generate [( t bpy)Pt(CH2CH2Ph)(η2-C2H4)][BAr′4] with k obs = 1.05(4) × 10–3 s–1 (23 °C, [C2H4] = 0.10(1) M). In the catalytic hydrophenylation of ethylene, substantial amounts of diethylbenzenes are produced, and experimental studies suggest that the selectivity for the monoalkylated arene is diminished due to a second aromatic C–H activation competing with ethylbenzene dissociation.

The rising atmospheric concentration of CO2 has motivated researchers to seek routes for improved utilization, increased mitigation, and enhanced sequestration of this greenhouse gas. Through a combination of bioinformatics, molecular modeling, and first-principles quantum mechanics the binding of carbon dioxide to proteins is analyzed. It is concluded that acid/base interactions are the principal chemical force by which CO2 is bound inside proteins. With respect to regular secondary structural elements, β-sheets show a marked preference for CO2 binding compared to α-helices. The data also support the inference that while either or both oxygens of CO2 are generally tightly bound in the protein environment, the carbon is much less “sequestered.” First principles and more approximate modeling techniques are assessed for quantifying CO2 binding thermodynamics.

The series of Pt II complexes [( x bpy)Pt(Ph)(THF)][BAr′ 4 ] ( x bpy =4,4′-X-2,2′-bipyridyl, X = OMe, t Bu, H, Br, CO 2 Et, NO 2 ; Ar′ = 3,5bis(trifluoromethyl)phenyl) are catalyst precursors for ethylene hydrophenylation.The bipyridyl substituent provides a tunable switch for catalyst selectivity that also has significant influence on catalyst activity and longevity. Less electron donating 4,4′-substituents increase the propensity toward styrene formation over ethylbenzene.

Expansion of the dipyridyl ligand from a fiveto six-membered chelate for Pt II -catalyzed ethylene hydrophenylation provides an enhancement of catalyst activity and longevity. Mechanistic studies of [(dpm)Pt(Ph)(THF)]-[BAr′ 4 ] [dpm = 2,2′-dipyridylmethane, and Ar′ = 3,5-(CF 3 ) 2 C 6 H 3 ] attribute the improved catalytic performance at elevated temperatures to a favorable change in entropy of activation with an increase in chelate ring size. The Pt II catalyst precursor [(dpm)Pt(Ph)(THF)][BAr′ 4 ] is among the most active catalysts for ethylene hydrophenylation by a non-acid-catalyzed mechanism.