ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

Supramolecular Self-Assembly of 1D and 3D Heterometallic Coordination Polymers with Triruthenium Building Blocks

Ru(3) (TSA)(6) (1; H(2) TSA=2-thiosalicylic acid), which bears six peripheral carboxylate groups and was isolated in the form [NEt(4) ](1.5) [Ru(3) (HTSA)(2) (TSA)(4) ](OAc)(0.5) ?3.5?H(2) O, serves as a building block for assembly of heterometallic coordination polymers. Treatment of 1 with [Fe(acac)(3) ] (acac=acetylacetonate) in EG/H(2) O (EG=ethylene glycol) afforded 1D Ru(3) -Fe coordination polymer 2 by means of the connection of the building block 1 through iron centers. Treatment of 1 with MnCl(2) in EG resulted in the formation of 1D Ru(3) -Mn(3) coordination polymer 3, which features self-assembled polynuclear linking units Mn(3) (OCH(2) CH(2) O)(3) , each of which contains a planar Mn(3) O(3) ring. By treating 1 with Gd(NO(3) )(3) and NaHCO(3) in EG, a 3D Ru(3) -Gd(6) coordination polymer 4 was obtained; this 3D coordination polymer features unprecedented Gd(6) (μ(3) -CO(3) )(4) units. The magnetic properties of 1-4, along with DFT calculations on the electronic structure of 1, are also described.     

Core level binding energy shifts of K and Cs adlayers on Ru(001)

Using synchrotron radiation from the VUV ring at NSLS and vacuum ultraviolet radiation from a HeI resonance lamp, we have recorded high resolution photoemission spectra of K and Cs overlayers on Ru(001). It is found that for “thin” multilayer coverages ( 3 ML) the K3p and Cs5p core levels exhibit three sets of core levels which can be assigned to interface, “bulkrd and surface emission in increasing binding energy. The results are discussed in terms of the nature of electronic interaction and a thermodynamic model. The K3p core level spin-orbit splitting is also resolved in these measurements for K in the condensed phase, for the first time with photoemission spectroscopy.     

Phosphonium-Ring-Fused Bicyclic Metallafuran Complexes of Ruthenium and Osmium

Metallafuran complexes with a fused five-membered phosphonium ring were synthesized from reactions between terminal ynones HC≡C(C=O)R and cis-[Ru/Os(dppm)₂Cl₂] (dppm=1,1-bis(diphenylphosphino)methane). A metal–vinylidene-involving pathway was found to be an energetically feasible formation mechanism for these complexes. These phosphonium-containing metallafurans, like many phosphonium-functionalized drugs, have the ability to induce mitochondrial dysfunction. They also exhibit stronger cytotoxicity against several human cancer cell lines in comparison with their metal precursors and the classic anticancer drug cisplatin. Overall, this work provides structural and mechanistic insights for the rational design of functional metallacycles via activation of alkynes by Ru^II and Os^II centers.     

Strongly Phosphorescent Neutral Rhenium(I) Isocyanoborato Complexes: Synthesis,Characterization, and Photophysical,Electrochemical, and Computational Studies

A new series of neutral isocyanoborato rhenium(I) diimine complexes [Re(CO)₃(N^N)(CNBR₃)], where N^N=bpy, 4,4′‐Me₂bpy, phen, 4,7‐Me₂phen, 2,9‐Me₂phen, 3,4,7,8‐Me₄phen; R=C₆F₅, C₆H₅, Cl, 4‐ClC₆H₄, 3,5‐(CF₃)₂C₆H₃, with various isocyanoborate and diimine ligands of diverse electronic and steric nature have been synthesized and characterized. The X‐ray crystal structures of six complexes have also been determined. These complexes displayed intense bluish green to yellow phosphorescence at room temperature in dichloromethane solution. The photophysical and electrochemical properties of these complexes had been investigated. To elucidate the electronic structures and transitions of these complexes, DFT and TD‐DFT calculations have been performed, which revealed that the lowest‐energy electronic transition associated with these complexes originates from a mixture of MLCT [dπ(Re)→π*(N^N)] and LLCT [π(CNBR₃)→π*(N^N)] transitions.     

Development of a broad toxicological screening technique for urine using ultra-performance liquid chromatography and time-of-flight mass spectrometry

Withdrawal of the support for the REMEDi HS drug profiling system has necessitated its replacement within our laboratories with an alternative broad toxicological screening technique. To this end, a novel method, based on ultra-performance liquid chromatography (UPLC) and time-of-flight (TOF) mass spectrometry, was developed for the routine analysis of urine samples. Identification was achieved by comparison of acquired data to libraries containing more than 300 common drugs and metabolites, and was based on a combination of retention time, exact mass and fragmentation patterns. Validation data for the method is presented and comprised an evaluation of the following parameters: precision; transferability of the methodology between the six collaborating laboratories; specificity; extraction recovery and stability of processed samples; matrix effects and sensitivity.This paper presents the benefits of supplementary fragmentation data with particular regard to increasing specificity and confidence of identification and its usefulness with overdosed samples. The utility of the method was assessed by the parallel analysis of 30 authentic urine samples using the REMEDi HS and UPLC-TOF. The latter provided enhanced detection, leading to the identification of twice as many drugs. Furthermore it did not miss any compounds that were identified by REMEDi HS. The UPLC-TOF findings were further verified by a combination of data from three other conventional screening techniques, i.e., GC-MS, HPLC-DAD and UPLC-MS/MS.     

Evolution of electronic structure and spectral evaluation in single-crystal Mn3O4 nanorods

Single-crystal Mn3O4 nanorods with tetragonal structure have been successfully prepared by a chemical reaction route. Transmission electron microscopy (TEM) and high-resolution TEM studies prove that the single-crystal Mn3O4 nanorod is smooth and straight, and that the geometrical shape is structurally perfect. We investigated the electronic characteristics of Mn3O4 nanorods by various spectral evaluations. The present study confirms that the hybridization between oxygen 2p and manganese 3d orbits plays an important role when considering electronic structures of Mn3O4 nanorods.     

Molecular surface generation using marching tetrahedra

A method is presented to generate and triangulate molecular surfaces rapidly. It is based on the ‘marching tetrahedra’ approach. The method is fast, simple and easy to implement. Our approach is not analytical in nature. Hence no special treatment is required for complications with singularity, degeneracy, or with self-intersecting re-entrant surfaces. A quick test for determining the solvent accessibility of a point in space forms an important part of the method. This test has potential use outside of the surface generation algorithm such as in molecular field analysis where the solvent accessibility of a point needs to be determined. The triangulated surface generated is suitable for molecular graphics display as well as boundary element continuum dielectric calculations. © 1998, Government of Canada. Exclusive worldwide publication rights in the article have been transferred to John Wiley & Sons, Inc. in perpetuity. J Comput Chem 19: 1268–1277, 1998