Ion implantation doping and electrical properties of high-temperature ladder polymers

We report the first ion implantation doping studies on high-temperature ladder polymers and show that insulting films of the benzimidazobenzophenanthroline-type ladder polymer (BBL) can be doped by boron, argon, and krypton implantation to conductivities as high as 224 S/cm at a dose of 4.0 × 10¹⁶/cm² while retaining the excellent mechanical properties of the pristine films. Effects of dose (ions/cm²) and beam current density (microamps/cm²) on electrical conductivity at fixed ion energies are reported. The temperature dependence of the conductivity indicates that the implanted ladder polymer films are semiconductors. Spatially selective implantation, creating regions of conducting lines in an insulating matrix, which suggests microelectronic device applications of the ladder polymers, is demonstrated.     

Synthesis, characterization, and in vitro evaluation of a potentially selective anticancer, mixed-metal [ruthenium(III)-platinum(II)] trinuclear complex

A new type of mixed-metal trinuclear complex containing platinum(II) and ruthenium(III) fragments that resemble both cisplatin and NAMI-A has been synthesized and characterized by IR, 1H NMR, elemental analysis, and X-ray crystallography. The water-soluble compound Na2{trans,cis,trans-[RuIIICl4(DMSO-S)(mu-pyz)]2PtIICl2} (AH-197, pyz = pyrazine) was assessed for its effects on DNA mobility and toxicity against human cancer cell lines. When compared to cisplatin and KP-1019 (which structurally resembles NAMI-A), IC50 results showed that AH-197 had an intermediate toxicity. When this data was coupled with a subsequent COMPARE evaluation (standard COMPARE queries resulted in insignificant correlation coefficients (<0.70) while very low COMPARE correlation coefficients were found in the matrix queries as well), AH-197 yielded a correlation coefficient of 0.19 when compared to cisplatin and 0.25 when compared to KP1019 indicating that AH-197 has a unique behavior.     

Conformer-Specific Dissociation Dynamics in Dimethyl Methylphosphonate Radical Cation

The dynamics of the dimethyl methylphosphonate (DMMP) radical cation after production by strong field adiabatic ionization have been investigated. Pump-probe experiments using strong field 1300 nm pulses to adiabatically ionize DMMP and a 800 nm non-ionizing probe induce coherent oscillations of the parent ion yield with a period of about 45 fs. The yields of two fragments, PO₂C₂H₇⁺ and PO₂CH₄⁺, oscillate approximately out of phase with the parent ion, but with a slight phase shift relative to each other. We use electronic structure theory and nonadiabatic surface hopping dynamics to understand the underlying dynamics. The results show that while the cation oscillates on the ground state along the P=O bond stretch coordinate, the probe excites population to higher electronic states that can lead to fragments PO₂C₂H₇⁺ and PO₂CH₄⁺. The computational results combined with the experimental observations indicate that the two conformers of DMMP that are populated under experimental conditions exhibit different dynamics after being excited to the higher electronic states of the cation leading to different dissociation products. These results highlight the potential usefulness of these pump-probe measurements as a tool to study conformer-specific dynamics in molecules of biological interest.     

Coherent Vibrational and Dissociation Dynamics of Polyatomic Radical Cations

The ultrafast dynamics of polyatomic radical cations contribute to important processes including energy transfer in photovoltaics, electron transfer in photocatalysis, radiation-induced DNA damage, and chemical reactions in the upper atmosphere and space. Probing these dynamics in the gas phase is challenging due to the rapid dissociation of polyatomic radical cations following electron removal, which arises from excess electronic excitation of the molecule during the ionization process. This Concept article introduces the reader to how the pump-probe technique of femtosecond time-resolved mass spectrometry (FTRMS) can overcome this challenge to capture coherent vibrational dynamics on the femtosecond timescale in polyatomic radical cations and enable the analysis of their dissociation pathways. Examples of FTRMS applied to three families of polyatomic radical cations are discussed.     

Sonoelectroanalytical detection of lead at a bare copper electrode

The sonochemically facilitated, mercury free detection of Pb²⁺ at a copper electrode has been investigated as a means of simplifying the quantification of this important analyte and to minimise the interference of copper ion. The procedure relies upon maximising the formation of Pb-Cu intermetallic compounds leading to the emergence of a single, easily quantifiable stripping signal. Linear responses to Pb²⁺ were obtained with a sensitivity comparable to that obtained at a bare glassy carbon electrode. Interference from Cu²⁺, Zn²⁺ and Cd²⁺ was assessed on the copper electrode with no appreciable change in the Pb²⁺ voltammetric profile observed. In contrast, bare glassy carbon showed a significant change in Pb²⁺ voltammetric profile as Cu²⁺ was added, due to the formation of intermetallic species.     

A labeling study of π-cycloheptatrienetricarbonylchromium(0)

Peaks of different intensities in the mass spectra of π-toluenetricarbonylchromium and π-cycloheptatrienetricarbonylchromium were studied by deuterium labeling of the latter compound. Incomplete hydrogen randomization in cycloheptatriene ligands preceding different reactions was observed, in contrast to the results for cycloheptatriene itself.