Luminescent cyanide coordination polymer based on {Mo6I8} and {Ag2(dppm)2} clusters: exceptional stability and efficient scintillation

Abstract

First metal–organic coordination polymer based on the [{Mo₆I₈}(CN)₆]²⁻ cluster anion was obtained using the salts Cs_1.3Na_0.7[{Mo₆I₈}(CN)₆]·2H₂O (1) and K[Ag(CN)₂], as well as bis(diphenylphosphino)methane (dppm), as precursors. In contrast to the previously reported coordination polymers based on octahedral cyanide cluster complexes, the 1D polymer [{Ag₂(dppm)₂}{Mo₆I₈}(CN)₆] (2) demonstrated an order of magnitude increase in the cluster-centred photoluminescence quantum yield (Φ_em) in the solid state at 300 K in comparison with the ionic salt 1. Moreover, 2 exhibits bright X-ray-induced emission, which is two orders of magnitude more intense than that of 1 and is characterized by a light yield of 10 800 photons per MeV. Therefore, 2 represents the first effective scintillating compound based on octahedral molybdenum clusters. The polymer has exceptional thermal, photo- and hydrolytic stability and exhibits minimal degradation upon X-ray irradiation, retaining its emission intensity following exposure to the dose of 2.2 × 10⁵ rad. It should be noted that this level of radiation resistance is superb even for inorganic scintillation materials. The high light yield and exceptional stability of the compound enabled us to use it to manufacture scintillation screens for X-ray visualisation. These screens provide a spatial resolution of up to 9 line pairs per mm, representing the first example of a scintillation device based on molybdenum clusters.