We report on investigations of reactions of tBu(2) Zn with 8-hydroxyquinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc aggregate [tBuZn(q)](3)(1(3)), the pentanuclear oxo cluster [(tBu)(3) Zn(5)(μ(4)-O)(q)(5)](2), and the tetranuclear hydroxo cluster [Zn(q)(2)](2)[tBuZn(OH)](2)(3). All compounds were characterized in solution by (1) H NMR, IR, UV/Vis, and photoluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density functional theory calculations were also carried out for these new Zn(II) complexes to rationalize their luminescence behavior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the corresponding single molecules leads to the formation of extended 3D networks with 1D open channels. Varying the stoichiometry, shape, and supramolecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close-packed crystal structure of 1(3) shows a redshifted emission maximum in comparison to the porous crystal structure of 2 and the THF-solvated structure of 3.

Quantitative subtractively normalized interfacial Fourier transform infrared reflection spectroscopy (SNIFTIRS) was used to determine the conformation and orientation of adsorbed sodium dodecyl sulfate (SDS) molecules adsorbed at the single crystal Au(111) surface. The SDS molecules form a hemimicellar/hemicylindrical (Phase I) structure for the range of potentials between -200 ≤ E < 450 mV and condensed (Phase II) film for electrode potentials ≥ 500 mV vs. Ag/AgCl. The SNIFTIRS measurements indicate that the alkyl chains within the two adsorbed states of SDS film are in the liquid-crystalline state rather than the gel state. However, the sulfate head group is in an oriented state in Phase I and is disordered in Phase II. The newly acquired SNIFTIR spectroscopy measurements were coupled with previous electrochemical, atomic force microscopy and neutron reflectivity data to improve the current existing models of the SDS film adsorbed on the Au(111) surface. The IR data supports the existence of a hemicylindrical film for SDS molecules adsorbed at the Au(111) surface in Phase I and suggests that the structure of the condensed film Phase II can be more accurately modeled by a disordered bilayer.

In this work, the enantioseparation of 15 structurally similar chiral solutes is studied, and analysis of the retention factors is performed using a genetic algorithm and multiple linear regression analysis technique. The present quantitative structure-enantioselective retention relationship model generated for retention factors' data has confirmed the importance of a number of descriptors altering the retention behavior and enantioselectivity of the studied compounds. Thus, fragment-based descriptor PSA, which encodes polar surface area, has confirmed the crucial role of heteroatoms in the retention behavior exhibited by pyrroliddin-2-ones. The presence of E(LUMO) descriptor, which represents a quantum-chemical property, has indicated the role of charge transfer interactions between the chiral stationary phase and enantiomers to retention factors, showing that lowest unoccupied molecular orbital energy is significantly different between enantiomers. The developed model exhibits a very good performance characterized by following statistical parameters: r(2) = 0.93 for training set and r(2) = 0.99 for the validation set. The selected three-variable model displays high predictive ability, catching the main factors affecting the enantioselectivity of studied chiral compounds, and therefore can be used for prediction of retention factors of other chiral compounds of similar structure to improve the separation process and so on. Chirality, 2011. © 2011 Wiley Periodicals, Inc.

In this study, a Au(111) electrode is functionalized with a monolayer of 1-thio-betha-D-glucose (Tg), producing a hydrophilic surface. A monolayer of Tg was formed on a Au(111) surface either by (1) potential-assisted deposition with the thiol in a supporting electrolyte or (2) passive incubation of a gold substrate in a thiol-containing solution. For each method, the properties of the Tg monolayer were investigated using cyclic voltammetry (CV), differential capacitance (DC), and chronocoulometry. In addition, electrochemical scanning tunneling microscopy (EC-STM) was used to obtain images of the SAM with molecular resolution. Potential-assisted assembly of Tg onto a Au(111) electrode surface was found to be complicated by oxidation of Tg molecules. The EC-STM images revealed formation of a passive layer containing honeycomb-like domains characteristic of a formation of S8 rings, indicating the S-C bond may have been cleaved. In contrast, passive self-assembly of thioglucose from a methanol solution was found to produce a stable, disordered monolayer of Tg. Since the passive assembly method was not complicated by the presence of a Faradaic process it is the method of choice for modifying the gold surface with a hydrophilic monolayer.

The surface of a gold electrode was functionalized with a hydrophilic monolayer of 1-thio-β-D-glucose formed by spontaneous self-assembly. The Langmuir-Blodgett/Langmuir-Schaefer (LB/LS) method was then used to assemble a bilayer onto the modified Au(111) surface. The bilayer lipid membrane (BLM) was separated from the Au(111) electrode surface by incorporating the monosialoganglioside GM1 into the inner leaflet of a bilayer composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and cholesterol. To make the inner leaflet, monolayers of GM1/DMPC/cholesterol with mole ratios of 1:6:3, 2:5:3, and 3:4:3 were used. The outer leaflet was composed of a 7:3 mole ratio of DMPC/cholesterol. Because of the amphiphilic properties of GM1, the hydrophobic acyl chains were incorporated into the BLM, whereas the large hydrophilic carbohydrate headgroups were physically adsorbed to the Au(111) electrode surface, creating a "floating" BLM (fBLM). This model contained a water-rich reservoir between the BLM and the gold surface. In addition, because of the bilayer being physically adsorbed onto the support, the fluidity of the BLM was maintained. The compression isotherms were measured at the air/water interface to determine the phase behavior and optimal transfer conditions. The images acquired using atomic force microscopy (AFM) and the force-distance measurements showed that the structure of the fBLM evolved with increasing GM1 content from 10 to 30 mol %, undergoing a transition from a corrugated to a homogeneous phase. This change was associated with a significant increase in bilayer thickness (from ∼5.3 to 7.3 nm). The highest-quality fBLM was produced with 30 mol % GM1.

Langmuir-Blodgett and Langmuir-Schaeffer methods were employed to deposit a mixed bilayer consisting of 90% of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 10% of gramicidin (GD), a short 15 residue ion channel forming peptide, onto a Au(111) electrode surface. This architecture allowed us to investigate the effect of the electrostatic potential applied to the electrode on the orientation and conformation of DMPC molecules in the bilayer containing the ion channel. The charge density data were determined from chronocoulometry experiments. The electric field and the potential across the membrane were determined through the use of charge density curves. The magnitudes of potentials across the gold-supported biomimetic membrane were comparable to the transmembrane potential acting on a natural membrane. The information regarding the orientation and conformation of DMPC and GD molecules in the bilayer was obtained from photon polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) measurements. The results show that the bilayer is adsorbed, in direct contact with the metal surface, when the potential across the interface is more positive than -0.4 V and is lifted from the gold surface when the potential across the interface is more negative than -0.4 V. This change in the state of the bilayer has a significant impact on the orientation and conformation of the phospholipid and gramicidin molecules. The potential induced changes in the membrane containing peptide were compared to the changes in the structure of the pure DMPC bilayer determined in earlier studies.

Volume changes corresponding to transitions between different phases of high-pressure argon gas hydrates were studied with a piston-cylinder apparatus at room temperature. Combination of these data with the data taken from the literature allowed us to obtain self-consistent set of data concerning the equations of state and compositions of the high-pressure hydrates of argon.

Potentiometric titrations of the cytochrome c oxidase (CcO) immobilized in a biomimetic membrane system were followed by two-dimensional surface-enhanced IR absorption spectroscopy (2D SEIRAS) in the ATR-mode. Direct electron transfer was employed to vary the redox state of the enzyme. The CcO was shown to undergo a conformational transition from a non-activated to an activated state after it was allowed to turnover in the presence of oxygen. Differences between the non-activated and activated state were revealed by 2D SEIRA spectra recorded as a function of potential. The activated state was characterized by a higher number of correlated transitions as well as a higher number of amino acids associated with electron transfer.

The bridging of hexanuclear mixed-valent carboxylate coordination clusters of the type [Mn(6)O(2)(O(2)CR)(10)](R = CMe(3); CHMe(2)) featuring a {Mn(II)(4)Mn(III)(2)(mu(4)-O)(2)} core by geometrically rigid as well as flexible spacer ligands such as pyrazine (pyz), nicotinamide (na), or 1,2-bis(4-pyridyl)ethane (bpe) results exclusively in one-dimensional (1D) coordination polymers. The formation of {[Mn(6)O(2)(O(2)CCMe(3))(10)(Me(3)CCO(2)H)(EtOH)(na)] x EtOH x H(2)O}(n)(1),{[Mn(6)O(2)(O(2)CCHMe(2))(10)(pyz)(3)] x H(2)O}(n)(2), and {[Mn(6)O(2)(O(2)CCHMe(2))(10)(Me(2)CHCO(2)H)(EtOH)(bpe)] x Me(2)CHCO(2)H}(n)(3) illustrates a surprising preference of the interlinked {Mn(6)} units toward 1D coordination chains. In the solid-state, the observed chain propagation axes are either colinear (1 and 3) or perpendicular (2), whereby crystal packing is further influenced by solvent molecules. Magnetic properties of these network compounds can be rationalized based on that the magnetism of discrete [Mn(6)O(2)(O(2)CR)(10)]-type coordination clusters with all-antiferromagnetic intramolecular exchange and weak antiferromagnetic intercluster coupling in 1, 2, and 3 follows the expected exchange coupling strength of the employed spacer linkers.