The new square-planar platinum-diimine-dithiolate compounds [Pt(mesBIAN)SS] have been synthesised {mesBIAN = bis(mesityl)biazanaphthenequinone; SS = 1,2-dithiooxalate (dto) , maleonitriledithiolate (mnt) , 1,2-benzenedithiolate (bdt) , 3,4-toluenedithiolate (tdt) and 1,3-dithia-2-thione-4,5-dithiolate (dmit) }, and the X-ray crystal structures of and determined. Cyclic voltammetry reveals that all the compounds form stable anions, and ESR spectroscopy of these anions shows that the SOMO is based upon the mesBIAN ligand; compounds also show a reversible oxidation wave in their CV. Computational studies reveal that charge-transfer processes from orbitals that are combinations of metal and dithiolate ligand to a mesBIAN pi-based LUMO are responsible for the low energy absorptions seen in the UV/visible spectra of these compounds, and that the reverse process is responsible for the observed room-temperature solution luminescence of [Pt(mesBIAN)Cl(2)] and , and . Compounds and , containing aromatic thiolates, were not found to luminesce under the same conditions. Resonance Raman experiments have shown the origin of band-broadening of the lowest-energy absorption band in the absorption spectra of to be due to vibronic structure within one electronic transition.
Synopsis
A nearly complete mandible of a large tetrapodomorph sarcopterygian from the Frasnian Alves Beds is studied with the aid of computed tomography. The absence of cosmine, a small parasymphysial dental plate bearing dentition that is discontinuous with that of the coronoids, and the presence of an elongated posterior coronoid that bears two fang pairs restrict placement of the tetrapodomorph from the Alves Beds to Tristichopteridae, and suggest that is a member of the clade that is sister to the anatomically primitive Givetian genus
Tristichopterus
. Taxa from this segment of tristichopterid phylogeny include the Givetian–Frasnian
Eusthenopteron
and Frasnian
Jarvikina
, but the tristichopterid from the Alves Beds is distinguished from both by the presence of an organized row of well-developed teeth on the posterior coronoid. This character has been proposed as a synapomorphy of taxa crownward of Trischopteridae, but is widely distributed among tetrapodomorph fishes. Our reinterpretation of lower jaw material of
Tinirau clackae
suggests this species is a member of the Tristichopteridae rather than the ‘Elpistostegalia’, and likely includes material assigned to a second species and genus of tetrapodomorph from the Red Hill site,
Bruehnopteron murphyi
. Proposal of a formal taxonomic name for the tristichopterid from the Alves Beds is withheld pending the discovery or analysis of further material from these deposits.
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