Superbroad near to mid infrared luminescence from closo-deltahedral Bi_5 ^3+ cluster in Bi_5(GaCl_4)_3

Closo-deltahedral Bi(5)(3+) cluster in Bi(5)(GaCl(4))(3), which can be synthesized in benzene by oxidizing bismuth metal either with BiCl(3) or GaCl(3), respectively, can absorb ultraviolet, visible and infrared lights, and luminesce superbroadly in near to mid infrared (NMIR) spectral range from 1 to 3μm at room temperature. Slight geometry change of the cluster can lead to the redshift of emission peak. These observations may initialize the development of Bi-based NMIR light sources with superbroad emission spectrum, where Bi(5)(3+) or similar polycationic species act as activators. Disputable crystal structure of Bi(5)(GaCl(4))(3) was redefined by classic Rietveld refining analysis. Consistent with crystallographic data, excitation, emission, temporal decay and time-resolved infrared emission spectra all reveal only one type of luminescent centers, viz. Bi(5)(3+), in the compound. And a new absorption of Bi(5)(3+) was found at ~1100nm.