Platinum chalcogenido MCM-41 analogues. High hexagonal order in mesostructured semiconductors based on Pt²⁺ and [Ge₄Q₁₀]^4- (Q = S, Se) and [Sn₄Se₁₀]^4- adamantane clusters

Highly periodic hexagonal honeycombs of platinum-germanium chalcogenide and platinumtin selenide frameworks were prepared by linking corresponding [Ge₄Q₁₀]^4- (Q = S, Se) and [Sn₄Se₁₀]^4- clusters with Pt²⁺ ions. The non-oxidic honeycombs designated as C_nPyPtGeQ and C_nPyPtSnSe were templated by the lyotropic liquid-crystalline phase of alkylpyridinium surfactant [C_nH_2n+1NC₅H₅]Br (C_nPyBr) with n= 12, 14, 16, 18, 20, and 22. Although the materials are amorphous at the microscale, they have crystalline mesoporosity with well-ordered and aligned surfactant-filled cylindrical pores. In addition to high mesoscopic order, the pore-pore separation is adjustable with the surfactant chain length (i.e., value of n). The quality of these materials, as judged by the degree of hexagonal order, rivals or exceeds that reported for the highest quality MCM-41 silicates. The materials have the lowest band gap reported so far for mesostructured chalcogenides solids, in the range 1.5 < E_g < 2.3 eV. The C_nPyPtGeS analogues show intense photoluminescence at 77 K when excited with light above the band gap.