A Fused Poly(truncated rhombic dodecahedron)-Containing 3D Coordination Polymer: A Multifunctional Material with Exceptional Properties.

The design of new and inexpensive metal-containing functional materials is of great interest. Herein is reported a unique thermochromic near-IR emitting coordination polymer, 3D-[CuI()], , which is formed when ArS(CH)SAr (, Ar = 4-CHOMe) reacts with 2 equiv of CuI in EtCN. In MeCN, ([CuI()(MeCN)], consisting of an alternating [-CuI--CuI--] chain where the CuI cubane units bear two metal-bound MeCN molecules, is formed. Heat-driven elimination of these MeCN's in solid also leads to through a predisposed organization of the CuI units prone to fusion after MeCN eliminations (i.e., a rare case of template effect). The structure exhibits parallel 1D-(CuI) chains, (-axis; designated 1D-[CuI]) as secondary building units (SBU) held together by parallel thioether ligands (,-axes), forming a nonporous 3D network. The structure of this 1D-[CuI] SBU is unprecedented and consists of a series of fused and twisted open CuI cubanes forming a fused poly(truncated rhombic dodecahedron). Unexpectedly, the compact 3D exhibits a solid-to-solid phase transition at 100 °C and a hysteresis of ∼20 °C. emits intensively (298 K: λ = 564 nm; Φ = 0.35), whereas presents a strongly red-shifted weaker emission (298 K: λ ∼ 740 nm, Φ < 0.0001). Moreover, , which is stable over long periods of time, exhibits thermochromism where the emission intensity of the near-IR band decreases significantly at the benefit of a ligand-centered phosphorescence at 415 nm. Altogether, these properties listed above make exceptional. The low-energy singlet and triplet excited states have been assigned to ligand/metal-to-ligand charge transfer based on DFT and TD-DFT computations.