William B. Connick

Structure of a crystalline vapochromic platinum(II) salt.

Square-planar cations of the orange form of [Pt(Me2bzimpy)Cl](PF6) x DMF [Me2bzimpy = 2,6-bis(N-methylbenzimidazol-2-yl)pyridine] stack along the b axis in a head-to-tail arrangement with short interplanar spacings (3.35 and 3.39 A). Long intermolecular Pt...Pt contacts [4.336(2) and 4.565(2) A] and comparatively short Me2bzimpy...Me2bzimpy distances are consistent with spectroscopic measurements for orange salts of Pt(Me2bzimpy)Cl+. The DMF solvent molecules line channels parallel to c, which may provide a conduit for vapor absorption. The crystals are vapochromic, changing from orange to violet upon exposure to acetonitrile vapor. The changes in spectroscopic properties accompanying vapor absorption are consistent with changes in intermolecular interactions between complexes.

Vapochromic and vapoluminescent response of materials based on platinum(II) complexes intercalated into layered zirconium phosphate

Novel materials based on platinum(II) complexes incorporated into zirconium phosphate (ZrP) frameworks exhibit rapid and reversible vapochromic/vapoluminescent response upon exposure to volatile organic compounds (VOCs). The pattern response is distinctly different than that of salts of the platinum complexes. These results suggest that the microenvironment of the ZrP can modulate the properties of vapochromic compounds.

Platinum(II) molecular triangle with a deep intramolecular cavity.

Depending on the conditions, the reaction of K 2PtCl 4 with 1,3-bis( N-pyrazolyl)benzene (bpzphH) yields either Pt(bpzph)Cl, [Pt(mu-bpzph)Cl] 3, or a mixture of these products. In the case of the C 3-symmetric trimer, each bpzph (-) ligand is bidentate with the metal bonded to a pyrazolyl group and to the phenyl group at the 6 position; the remaining pyrazolyl group bridges to an adjacent platinum center. The crystal structure confirms that each complex is chiral with an unusually deep (approximately 8 A) intramolecular cavity; enantiomeric pairs of trimers encapsulate the diethyl ether solvate. NMR studies establish that the trimer exhibits excellent thermal and kinetic stability. Substitution of the chloride ligands provides a strategy for elaborating the macrocycle.

Interaction of SbCl52- and Thioether Groups at the Open Coordination Sites of Platinum(II) Diimine Complexes

In the solid-state, the approximately square planar cation in orange crystals of [Pt(NO(2)phen)(ttcn)](PF(6))(2) (NO(2)phen = 5-nitro-1,10-phenanthroline; ttcn = 1,4,7-trithiacyclononane) has a short apical Pt...S(ttcn) distance (2.9415(15) A). In acetonitrile solution, the electronic spectrum shows a long-wavelength absorption band (412 nm; 2200 M(-1) cm(-1)), consistent with the notion that the axial Pt...S(ttcn) interactions stabilize states having metal-to-ligand charge-transfer (MLCT) character. Reaction with the hexachloroantimonate(V) salt of tris(4-bromophenyl)aminium (TBPA(+)) results in complex redox chemistry, involving the platinum complex, SbCl(5)(2-) and TBPA(+). In the case of Pt(bpy)(ttcn)(2+), orange-yellow crystals of [Pt(bpy)(ttcn)](2)(Sb(4)Cl(16)) were isolated from the reaction, whereas the reaction with Pt(NO(2)phen)(ttcn)(2+) consistently yielded red crystals of [Pt(NO(2)phen)(ttcn)](SbCl(5)) x 2 CH(3)CN. In the latter case, the geometry of the cation, including the apical Pt...S(ttcn) distance (2.9390(12) A), is very similar to that of the PF(6)(-) salt. However, the basal plane of each square pyramidal SbCl(5)(2-) opposes the nearly parallel coordination plane of an adjacent Pt(NO(2)phen)(ttcn)(2+) complex, resulting in an unusually short intermolecular Pt...Sb distance of 3.4259(3) A. The longest wavelength maximum in the diffuse reflectance spectrum and the solid-state emission maximum are shifted by approximately 1200 cm(-1) and approximately 700 cm(-1), respectively, to the red of those of the PF(6)(-) salt, consistent with perturbation of the complexs electronic structure because of the Pt...Sb interaction.

X-ray and synchrotron diffraction studies of 2-(pyridin-2-yl)-1,10-phenanthroline in the role of ligand for two copper polymorphs or hydrogen bonded with 2,2,6,6-tetramethyl-4-oxopiperidinium hexafluorophosphate.

Different extended packing motifs of dichlorido[2-(pyridin-2-yl)-1,10-phenanthroline]copper(II), [CuCl2(C17H11N3)], are obtained, depending on the crystallization conditions. A triclinic form, (I), is obtained from dimethylformamide-diethyl ether or methanol, whereas crystallization from dimethylformamide-water yields a monoclinic form, (II). In each case, the Cu(II) centre is in a five-coordinate distorted square-pyramidal geometry. The extended packing for both forms can be described as a highly offset π-stacking arrangement, with interlayer distances of 3.674 (3) and 3.679 (3) Å for forms (I) and (II), respectively. The reaction of diprotonated Pt(tmpip2NCN)Cl [tmpip2NCN = 2,6-bis(2,2,6,6-tetramethylpiperidylmethyl)benzyl] with AgPF6 under acidic conditions, followed by the addition of 2-(pyridin-2-yl)-1,10-phenanthroline, results in a hydrogen-bonded cocrystal, 2,2,6,6-tetramethyl-4-oxopiperidinium hexafluorophosphate-2-(pyridin-2-yl)-1,10-phenanthroline (1/1), C9H18NO(+)·PF6(-)·C17H11N3, (III). The extended packing maximizes π-π interactions in a parallel face-to-face arrangement, with an interlayer stacking distance of 3.4960 (14) Å.

Radio-fluorogenic dosimetry with violet diode laser-induced fluorescence

A set of experiments is described with radio-fluorogenic detectors and violet diode lasers. Radio-fluorogenic dosimetry is the measurement of absorbed dose by quantification of fluorescent products formed in response to ionizing radiation. Relative dosimetry was accomplished with 405nm violet diode laser-induced fluorescence (LIF) and digital imaging. Aqueous and gelatin-based solutions of radio-fluorogenic detectors were fabricated, irradiated with medical radiation devices, and pixel intensity values of digital images analyzed. The potential to use RFD to characterize spatial dose distributions with violet diode LIF is demonstrated.

Radio-Fluorogenic Gel Dosimetry with Coumarin

Gel dosimeters are attractive detectors for radiation therapy, with properties similar to biological tissue and the potential to visualize volumetric dose distributions. Radio-fluorogenesis is the yield of fluorescent chemical products in response to energy deposition from ionizing radiation. This report shares the development of a novel radio-fluorogenic gel (RFG) dosimeter, gelatin infused with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission following ultra-violet (UV) to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated. The response of the RFG was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship independent of energy and type, with a dose-rate dependency. This report demonstrates increased photo-yield with high pH and the utility of gelatin-RFG for phantom studies of radiation dosimetry.

Measurements of plutonium, 237Np, and 137Cs in the BCR 482 lichen reference material

Abstract Select anthropogenic radionuclides were measured in lichen reference material, BCR 482. This material was originally collected in Axalp, Switzerland in 1991 and is composed of the epiphytic lichen Pseudevernia furfuracea. Samples from three separate bottles of BCR 482 were analyzed for uranium, neptunium, and plutonium isotopes by inductively coupled plasma mass spectrometry and analyzed for 137Cs by gamma-ray spectrometry. The isotopic composition of the radionuclides measured in BCR 482 suggests contributions from both global fallout resulting from historical nuclear weapons testing and more volatile materials released following the Chernobyl accident.

Chapter 9:Variable-pressure luminescence and Raman spectroscopy of molecular transition metal complexes: spectroscopic effects originating from small, reversible structural variations

The past ten years have seen a significantly increasing number of published crystal structures for molecular transition metal complexes at variable pressure, providing quantitative information on structural variations. Spectroscopic measurements at variable pressure have been reported over the past 60 years for a variety of complexes, but luminescence measurements were mostly limited to intense signals until early in this century. The combination of variable-pressure structure variations with spectroscopic trends can lead to detailed new insight on a variety of aspects of electronic structure. This approach holds promise for the in-depth study of many categories of functional materials.