Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen.

The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1'H-indol-3'-yl)maleimide and 4-methyl-3-(1'H-indol-3'-yl)maleimide, are investigated. The bromo derivative was crystallized and its X-ray structure was determined. Both compounds are strongly colored while their separate components (indole and maleimide) absorb in the UV region only.

Intraresidue distribution of energy in proteins.

Boltzmann-like distributions appear in many properties and energy-related quantities of proteins. A few examples are hydrophobicity, various types of side-chain/side-chain interactions, proline isomerization, hydrogen bonds, internal cavities, interactions at the level of specific atom types, and the propensity of the phi/'phi' ratio. Here, we conjecture that the Boltzmann hypothesis also holds for the intra-residue energy distribution.

Unexpected photophysical properties of symmetric indolylmaleimide derivatives.

Arcyriarubin A and arcyriaflavin A, two strongly emissive and intensely colored natural products containing both two indoles and a maleimide unit, are investigated (in the flavin the two indole moieties are coupled by a cyclization). The photophysical properties of these compounds were studied in several solvents using UV-vis absorption, steady-state and time-resolved emission, nano- and femtosecond transient absorption spectroscopy. Furthermore, the effect of complexation with zinc(II) 1,4,7,11-tetraazacyclododecane on the photophysical properties of these natural products has been investigated.

Clay-fulleropyrrolidine nanocomposites.

In this work, we describe the insertion of a water-soluble bisadduct fulleropyrrolidine derivative into the interlayer space of three layered smectite clays. The composites were characterized by a combination of powder X-ray diffraction, transmission electron microscopy, X-ray photoemission and FTIR spectroscopies, and laser flash photolysis measurements. The experiments, complemented by computer simulations, give insight into the formation process, structural details, and properties of the fullerene/clay nanocomposites.

Incorporation of fullerene derivatives into smectite clays: a new family of organic-inorganic nanocomposites.

Three fulleropyrrolidine derivatives, characterized by the presence of positive charges, were introduced in the interlayer space of montmorillonite. The composites were characterized by powder X-ray diffraction and differential thermal and thermogravimetric (DTA-TGA) analysis, in conjunction with FTIR, UV-Vis, Raman, and (57)Fe-Mössbauer spectroscopies. Organophilic derivatives were intercalated into organically modified clays, while water-soluble fulleropyrrolidines were introduced into the clay galleries through ion exchange.

Modulation of the reduction potentials of fullerene derivatives.

The cyclic voltammetric (CV) study of a series of novel bisfulleropyrrolidines (3) and bisfulleropyrrolidinium ions (4) is reported. The eight possible stereoisomers of each series were systematically investigated under strictly aprotic conditions that allowed the observation of up to four and five subsequent reversible reductions in 3 and 4, respectively. Because of the stabilizing effect of positive charges, a significant enhancement of the electronegative properties was observed in 4.

Large enhancement of the nonlinear optical response of reduced fullerene derivatives.

The third-order nonlinear optical properties of fulleropyrrolidine and its salt as well as their reduced forms are investigated. Upon reduction, the response increases by up to, and sometimes more than, three orders of magnitude, giving values comparable to the largest ever reported. Calculations and experiments provide a coherent picture for the nonlinear optical properties of these new materials.

Switching "on" and "off" the expression of chirality in peptide rotaxanes.

The hydrogen-bond-directed synthesis, X-ray crystal structures, and optical properties of the first chiral peptide rotaxanes are reported. Collectively these systems provide the first examples of single molecular species where the expression of chirality in the form of a circular dichroism (CD) response can selectively be switched "on" or "off", and its magnitude altered, through controlling the interactions between mechanically interlocked submolecular components. The switching is achievable both thermally and through changes in the nature of the environment.