Latent fingermark development on fired and unfired brass ammunition under controlled and blind conditions.

There has been growing interest in the Foster+Freeman RECOVER® Latent Fingerprint Technology system to develop fingermarks from fired ammunition. Over a six-month period, 1540 fingermarks were deposited on brass.223 ammunition, the majority of which were then fired after different time intervals. Samples were subjected to a cleaning protocol and/or processed with disulfur dinitride, cyanoacrylate/Brilliant Yellow 40, and/or vacuum metal deposition. Overall, 121 out of 1304 (9.3%) of natural fingermarks deposited were deemed identifiable post-firing and processing. This translated to 102 out of 652 (15.6%) of fired cartridges having identifiable fingermarks. A pseudo-operational study, which involved processing 1000 fired brass ammunition of various caliber using disulfur dinitride with and without a cleaning protocol, was conducted; only 18 (1.8%) comparable fingermarks were developed. This study demonstrates the need for more robust research involving this challenging substrate and novel technology, with which several issues were identified.

Preparation of a Ytterbium-tagged Gunshot Residue Standard for Quality Control in the Forensic Analysis of GSR.

Preparation of a ytterbium-tagged gunshot residue (GSR) reference standard for scanning electron microscopy and energy dispersive X-ray spectroscopic (SEM-EDS) microanalysis is reported. Two different chemical markers, ytterbium and neodymium, were evaluated by spiking the primers of 38 Special ammunition cartridges (no propellant, no projectile) and discharging them onto 12.7 mm diameter aluminum SEM pin stubs. Following SEM-EDS microanalysis, the majority of tri-component particles containing lead, barium, and antimony (PbBaSb) were successfully tagged with the chemical marker. Results demonstrate a primer spiked with 0.75% weight percent of ytterbium nitrate affords PbBaSb particles characteristic of GSR with a ytterbium inclusion efficiency of between 77% and 100%. Reproducibility of the method was verified, and durability of the ytterbium-tagged tri-component particles under repeated SEM-EDS analysis was also tested. The ytterbium-tagged PbBaSb particles impart synthetic traceability to a GSR reference standard and are suitable for analysis alongside case work samples, as a positive control for quality assurance purposes.

New phenoxido-bridged quasi-tetrahedral and rhomboidal [Cu4] compounds bearing µ4-oxido or µ(1,1)-azido ligands: synthesis, chemical reactivity, and magnetic studies.

[Cu(2)(µ(4)-O)Cu(2)] and [Cu(2)(µ(1,1)-N(3))(4)Cu(2)] geometrical arrangements are found in a new family of tetranuclear copper(II) complexes: [Cu(4)(µ(4)-O)(µ-cip)(2)Cl(4)] (1), [Cu(4)(µ(4)-O)(µ-cip)(2)(µ(1,3)-O(2)CPh)(4)]·2CH(3)OH (2·2CH(3)OH), and [Cu(4)(µ(1,1)-N(3))(4)(µ-cip)(2)(N(3))(2)]·DMF (3·DMF) [Hcip = 2,6-bis(cyclohexyliminomethylene)-4-methylphenol; CH(3)OH = methanol; DMF = dimethylformamide]. These complexes have been characterized by X-ray crystallography, and their magnetic properties have been studied. 1 and 2 form quasi-tetrahedral [Cu(4)(µ(4)-O)] complexes, and 3 is the first example of a rhomboidal [Cu(4)(µ(1,1)-N(3))] compound. Formation of the [Cu(4)] compounds is achieved via ligand-exchange reactions. The relative binding strength of the three ancillary ligands as N(3)(-) > PhCO(2)(-) > Cl(-) has been demonstrated from the core-conversion and peripheral ligand-exchange reactions. For the three complexes, the magnetic susceptibility measurements in the range of 1.8-300 K have been performed and modeled using two isolated S = (1)/(2) dimers based on the spin Hamiltonian H = -2J{S(Cu,1)·S(Cu,2)} with J/k(B) = -513, -340, and -315 K for 1-3, respectively (where J is the exchange constant through the oxido-phenoxido and azido-phenoxido bridges, respectively).

New mu(4)-oxido-bridged copper benzoate quasi-tetrahedron and bis-mu(3)-hydroxido-bridged copper azide and copper thiocyanate stepped cubanes: core conversion, structural diversity, and magnetic properties.

[Cu(2)(mu(4)-O)Cu(2)] and [Cu(2)(mu(3)-OH)(2)Cu(2)] geometrical arrangements are found in a new family of tetranuclear complexes: [Cu(4)(mu(4)-O)(mu-bip)(2)(mu-O(2)CPh)(4)].0.5CH(2)Cl(2) (1.0.5CH(2)Cl(2)), [Cu(4)(mu(3)-OH)(2)(mu-bip)(2)(N(3))(4)] (2), and [Cu(4)(mu(3)-OH)(2)(mu-bip)(2)(NCS)(4)(DMF)(2)] (3.2DMF) [Hbip = 2,6-bis(benzyliminomethyl)-4-methylphenol; DMF = dimethylformamide]. These complexes have been characterized by X-ray crystallography, and their magnetic properties have been studied. Complex 1 reacts with azide and thiocyanate anions, leading to 2 and 3 with a change of the [Cu(4)(mu(4)-O)] core into [Cu(4)(mu(3)-OH)(2)] units. These compounds are new examples of [Cu(4)] complexes where Cu(II) ions are connected by two types of water-derived ligands: oxide and hydroxide. Formation of these [Cu(4)] complexes can be controlled by changing the bridging ligands, which allows an effective tuning of the self-assembly. The study of the magnetic properties reveals that these complexes exhibit strong intramolecular antiferromagnetic interactions to yield a S(T) = 0 ground state. For the three complexes, the temperature dependence of the magnetic susceptibility was fitted using a model with two isolated S = 1/2 dimers based on the H = -2J{S(Cu,1).S(Cu,2)} spin Hamiltonian with J/k(B) = -289 K for 1; J/k(B) = -464 and -405 K for 2 and 3, respectively (where J is the exchange constant through the oxido-phenoxido or hydroxido-phenoxido bridges, respectively).

Manipulating the crystal packing of pyDTDA radical ligand coordination complexes with Mn(ii) and Ni(ii).

The synthesis of 4'-CN, 5'-CN and 5'-Br substituted pyDTDA neutral radical bidentate ligands is reported (pyDTDA = 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl). The Ni(hfac)(2) and Mn(hfac)(2) coordination complexes of both cyano substituted ligands, and the Mn(hfac)(2) coordination complex of the bromo substituted ligand, have been prepared and the crystal packing of these is compared (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). Unlike the previously reported Mn(hfac)(2)(pyDTDA), the Mn(hfac)(2)(4'-CN-pyDTDA) complex does not form dimers in the solid-state making it possible to measure the magnetic coupling between the unpaired electrons on the coordinated Mn(ii) ion and the unpaired electron on the radical ligand by SQUID magnetometry; J/k(B) = -74(1) K, using H = -2J{S(Mn).S(Rad)} and g(av.) = 2.01.

Two edge-sharing MnII4MnIII6 supertetrahedra give an anisotropic S = 28 +/- 1 MnII6MnIII11 complex.

A complex with a [Mn(II)(6)Mn(III)(11)] core results via formal fusion of two isotropic Mn(II)(4)Mn(III)(6) supertetrahedra along a common edge leading to a high spin ground state anisotropic system showing Mvs. H hysteresis loops below 1 K.

Ni(II) and hs-Fe(II) complexes of a paramagnetic thiazyl ligand, and decomposition products of the iron complex, including an Fe(III) tetramer.

Synthesis and structural, magnetic and electrochemical characterization of the Ni(hfac) 2(pyDTDA) and the Fe(hfac) 2(pyDTDA) complexes are reported (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-; pyDTDA = 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl). Unlike the previously reported Mn(II) and Cu(II) complexes, but similar to the Co(II) complex, the Ni(II) and Fe(II) complexes are not dimerized in the solid state, allowing for magnetic coupling between the metal ion and paramagnetic ligand to be readily obtained from solid state magnetic measurements: Ni complex, J/k B = +132(1) K, using H = -2 J{ S Ni. S Rad} and g Ni = 2.04(2) and g Rad = 1.99(2); Fe complex, J/k B = -60.3(3) K, using H = -2 J{ S Fe. S Rad} and g av = 2.11(2). The iron complex is unusually unstable. A thermal decomposition product is isolated wherein the coordinated pyDTDA ligand appears to have been transformed into a coordinated 2-(2'-pyridyl)-4,6-bis(trifluoromethyl)pyrimidine. The iron complex also yields a solution decomposition product in the presence of air that is best described as an oxygen bridged iron(III) tetramer with two hfac ligands on each of three iron atoms and two oxidized pyDTDA ligands chelated on the fourth.

Mn(II) and Cu(II) complexes of a dithiadiazolyl radical ligand: monomer/dimer equilibria in solution.

Complexes of the 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl radical bidentate ligand with bis(hexafluoroacetylacetonato)manganese(II) and with bis(hexafluoroacetylacetonato)copper(II) have been prepared. Unlike the previously reported cobalt(II) complex, these complexes form dimers via intermolecular S...S contacts in the solid state. The spectroscopic and magnetic properties of these species in the solid state and in solution are reported and compared to the previously reported Co(II) complex, with emphasis on the elucidation of the a monomer/dimer equilibrium in the solution. The electrochemical properties of these species in solution are also presented and discussed.

Dinuclear cobalt bis(dioxolene) complex exhibiting two sequential thermally induced valence tautomeric transitions.

4,6-Di-2'-pyridylpyrimidine is employed as a bis(diimine) ligand bridging two cobalt bis(dioxolene) centers. The thermally induced valence tautomeric transitions of these two metal centers are coupled through the ligand. The result is that sequential switching from high-spin Co(II) to low-spin Co(III) of one center, followed by the onset of switching of the other center at lower temperature, is observed in a solid amorphous thin film by IR absorption spectroscopy.

Design and synthesis of a 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl cobalt complex.

The 4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl neutral radical 1 has been prepared for use as a spin-bearing bidentate ligand. The coordination of this ligand to bis(hexafluoroacetylacetonato)cobalt affords a thermally stable complex 2. Magnetic susceptibility measurements of the crystalline complex indicate ferromagnetic coupling between the ligand-centered spin and the unpaired electrons of the high-spin Co(II).