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

Abstract

Highly periodic hexagonal honeycombs of platinum-germanium chalcogenide and platinum-tin selenide frameworks were prepared by linking corresponding [Ge(4)Q(10)](4)(-) (Q = S, Se) and [Sn(4)Se(10)](4)(-) clusters with Pt(2+) ions. The non-oxidic honeycombs designated as C(n)PyPtGeQ and C(n)PyPtSnSe were templated by the lyotropic liquid-crystalline phase of alkylpyridinium surfactant [C(n)H(2)(n)(+1)NC(5)H(5)]Br (C(n)PyBr) 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(n)PyPtGeS analogues show intense photoluminescence at 77 K when excited with light above the band gap.