Solid-State Step-Scan FTIR Spectroscopy of Binuclear Copper(I) Complexes

The structure in the ground and excited electronic state of two binuclear CuI N-heterocyclic phosphine complexes that are promising for implementation in organic light-emitting diodes is investigated by a combination of the time-resolved step-scan FTIR technique and quantum chemical calculations at the DFT level of theory. In contrast to the usual application of step-scan FTIR spectroscopy in solution, the herein-presented analyses are performed in a solid phase, that is, the CuI complexes are embedded in a KBr matrix (KBr pellet). The application of solid-state time-resolved step-scan FTIR spectroscopy is of great importance for transition metal complexes, since their photophysical properties often change on moving from solid to dissolved samples. The efficient applicability of the solid-state step-scan technique in a KBr matrix is demonstrated on the chosen CuI reference systems on nano- and microsecond timescales with an excitation wavelength of 355 nm. By comparison with theoretical results, the structure of the complexes in the electronic ground and lowest-lying electronically excited state can be determined.