A simple model is described with which the entire force versus penetration behavior of indentation with a sphere, during loading and unloading, may be simulated from knowledge of the four test material parameters, Young's modulus, Poisson's ratio, flow stress at the onset of full plastic flow and strain hardening index, and the elastic properties of the indenter. The underlying mechanisms are discussed and the predictions of the model are compared with data produced by an ultra low load, penetration measuring instrument.

Pt(trpy)Cl+, where trpy denotes 2,2':6',2' '-terpyridine, is a versatile binding agent but has a limited photochemistry due to a short excited-state lifetime. However, this work shows that the introduction of aryl substituents at the 4' position of the trpy ligand drastically alters the picture. For the substituents phenyl, p-methoxyphenyl, 1-naphthyl, 2-naphthyl, 9-phenanthrenyl, and 1-pyrenyl, the ligand abbrevations are 4'-Ph-T, 4'-pMeOPh-T, 4'-Npl-T, 4'-Np2-T, 4'-Phe9-T, and 4'-Pyre1-T, respectively. Techniques utilized include electrochemistry as well as absorption and emission spectroscopies. While the lowest energy excited states of Pt(4'-Ph-T)Cl+ and the parent complex Pt(trpy)Cl+ exhibit mainly metal-to-ligand charge-transfer (MLCT) character, the emitting state takes on aryl-to-trpy intraligand charge-transfer (ILCT) character as the substituents become more electron-donating. Studies of Zn(trpy)Cl2, its aryl-substituted analogues, and the free ligands themselves provide information about the relative energies of participating ILCT and intraligand 3pi-pi excited states. Even though the emission energy decreases when larger aryl groups are present, the emission lifetime increases all the way from 85 ns for Pt(4'-Ph-T)Cl+ to 64 micros for Pt(4'-Pyre1-T)Cl+. (Data from deoxygenated, room-temperature dichloromethane solution.) Intraligand character appears to dominate in the case of Pt(4'-Pyre1-T)Cl+, which is unique in the series in that it exhibits singlet and triplet emissions in solution. In aerated solution the complex shows prompt as well as delayed fluorescence. Finally, studies in donor media establish that the introduction of intraligand character inhibits solvent-induced exciplex quenching.

The stress/strain behavior of bulk material is usually investigated in uniaxial tension or compression; however, these methods are not generally available for very small volumes of material. Submicrometer indentation using a spherical indenter has the potential for filling this gap with, possibly, access to hardness and elastic modulus profiles, representative stress/strain curves, and the strain hardening index. The proposed techniques are based on principles well established in hardness testing using spherical indenters, but not previously applied to depth-sensing instruments capable of measurements on a submicrometer scale. These approaches are now adapted to the analysis of data obtained by stepwise indentation with partial unloading, a technique that facilitates separation of the elastic and plastic components of indentation at each step and is able to take account of the usually ignored phenomena of “piling up” and “sinking in”.

The crystal structure of [Pt(trpy)(MeCN)](SbF6)2, where trpy denotes 2,2‘:6‘,2‘‘-terpyridine, shows that the platinum complex packs as a monomer; however, the 3π−π* emission of the solid occurs at surprisingly long wavelengths at room temperature. At lower temperatures new, shorter-wavelength maxima appear. Of the known salts with the composition [Pt(trpy)Cl]A, the A = SbF6 - system is the lone example that exhibits a temperature-independent emission maximum. In these platinum(II) terpyridines, energy migration to defects or trap sites is one of the phenomena responsible for the temperature dependence of the solid-state emission spectrum. If trap emission is evident, the low-temperature spectral data are most representative of the bulk material.