Interpreting Effects of Structure Variations Induced
by Temperature and Pressure on Luminescence Spectra of Platinum(II)
Bis(dithiocarbamate) Compounds
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Abstract
Luminescence spectra of two square-planar
dithiocarbamate complexes of platinum(II) with different steric bulk,
platinum(II) bis(dimethyldithiocarbamate) (Pt(MeDTC)<sub>2</sub>)
and platinum(II) bis(di(<i>o</i>-pyridyl)dithiocarbamate)
(Pt(dopDTC)<sub>2</sub>), are presented at variable temperature and
pressure. The spectra show broad d–d luminescence transitions
with maxima at approximately 13500 cm<sup>–1</sup> (740 nm).
Variations of the solid-state spectra with temperature and pressure
reveal intrinsic differences due to subtle variations of molecular
and crystal structures, reported at 100 and 296 K for Pt(dopDTC)<sub>2</sub>. Luminescence maxima of Pt(MeDTC)<sub>2</sub> shift to higher
energy as temperature increases by +320 cm<sup>–1</sup> for
an increase by 200 K, mainly caused by a bandwidth increase from 3065
to 4000 cm<sup>–1</sup> on the high-energy side of the band
over the same temperature range. Luminescence maxima of Pt(dopDTC)<sub>2</sub> shift in the opposite direction by −460 cm<sup>–1</sup> for a temperature increase by 200 K. The bandwidth of approximately
2900 cm<sup>–1</sup> does not vary with temperature. Both ground
and emitting-state properties and subtle structural differences between
the two compounds lead to this different behavior. Luminescence maxima
measured at variable pressure show shifts to higher energy by +47
± 3 and +11 ± 1 cm<sup>–1</sup>/kbar, for Pt(MeDTC)<sub>2</sub> and Pt(dopDTC)<sub>2</sub>, respectively, a surprising difference
by a factor of 4. The crystal structures indicate that decreasing
intermolecular interactions with increasing pressure are likely to
contribute to the exceptionally high shift for Pt(MeDTC)<sub>2</sub>
