Londesborough, Michael G. S. ;
Dolanský, Jiří ;
Cerdán, Luis ;
Lang, Kamil ;
Jelínek, Tomáš ;
Oliva, Josep M. ;
Hnyk, Drahomír ;
Roca‐Sanjuán, Daniel ;
Francés‐Monerris, Antonio ;
Martinčík, Jiří ;
Nikl, Martin ;
Kennedy, John D.
Thermochromic Fluorescence from B18H20(NC5H5)2: An Inorganic–Organic Composite Luminescent Compound with an Unusual Molecular Geometry
Beschreibung:
B18H20(NC5H5)2 is a rare example of two conjoined boron hydride subclusters of nido and arachno geometrical character. At room temperature, solutions of B18H20(NC5H5)2 emit a 690 nm fluorescence. In the solid state, this emission is shifted to 620 nm and intensifies due to restriction of the rotation of the pyridine ligands. In addition, there is a thermochromicity to the fluorescence of B18H20(NC5H5)2. Cooling to 8 K engenders a further shift in the emission wavelength to 585 nm and a twofold increase in intensity. Immobilization in a polystyrene thin‐film matrix results in an efficient absorption of pumping excitation energy at 414 nm and a 609 nm photostable fluorescence. Such fluorescence from polystyrene thin films containing B18H20(NC5H5)2 can also be stimulated by emission from the highly fluorescent borane anti‐B18H22 via energy transfer mechanisms. Polystyrene thin‐film membranes doped with 1:1 mixtures of anti‐B18H22 and B18H20(NC5H5)2 thus emit a 609 nm fluorescence and absorb light across more than 300 nm (250–550 nm); this is a significant spectral coverage possibly useful for luminescent solar concentrators. B18H20(NC5H5)2 is fully structurally characterized using NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction analysis, and its ground‐state and excited‐state photophysics are investigated with UV–vis spectroscopy and quantum‐chemistry computational methods.