Transition metal complexes of β-dtpy (1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide) are spectrally similar to metallophthalocyanines (derivatives of porphyrin) but with the advantage of being D 2 h instead of D 4 h so that many degenerate electronic transitions are identifiable separately. We have prepared and characterized Fe(β-dtpy)2·4THF, whose crystal structure allows three spectral polarizations to be measured. We have assigned the visible and ultraviolet transitions that correspond to the Q and Soret regions of porphyrinic complexes; these assignments differ markedly from the traditional “four-orbital” model. The secondary Q peak (R) is a separate electronic transition rather than a vibronic component, and the Soret transition has been reassigned.

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We used high-pressure grown GaN single crystal substrates to fabricate dislocation free optoelectronic devices like light emitting diodes and laser diodes structures. The latter ones demonstrated laser action under optical pumping condition with the threshold of about 200 kW/cm2 at room temperature. In the present paper we would focus on the specific aspects of the homoepitaxial growth by MOVPE method including epi-ready substrate preparation and surface polarity choice. We believe that our results demonstrate clearly the feasibility of device fabrication based on high-pressure grown GaN bulk crystals.