Solid-State Structures and Photoluminescence of Lamellar Architectures of Cu(I) and Ag(I) Paddlewheel Clusters with Hydrogen-Bonded Polar Guests

Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu-6(Hmna)(6)]center dot 7DMF (1 center dot 7DMF) and [Ag-6(Hmna)(6)]center dot 8DMSO (2 center dot 8DMSO), where H(2)mna = 2-mercaptonicotininc acid, DMF = N,N'-dimethylformamide, and DMSO = dimethyl sulfoxide. The solvated clusters, together with their fully desolvated forms 1 and 2, have been characterized by FTIR, UV-Vis diffuse reflectance spectroscopy, TG-DTA analysis, and DFT calculations. Crystal structures of two solvated clusters 1 center dot 7DMF and 2 center dot 8DMSO have been unambiguously determined by single-crystal X-ray diffraction analysis. Six carboxylic groups appended on the clusters trap solvent guests, DMF or DMSO, through H-bonds. As a result, alternately stacked lamellar architectures comprising of a paddlewheel cluster layer and H-bonded solvent layer are formed. Upon UV illumination (lambda(ex) = 365 nm), the solvated hexasilver(I) cluster 2 center dot 8DMSO gives intense greenish-yellow photoluminescence in the solid state (lambda(PL) = 545 nm, phi(PL) = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1 center dot 7DMF displays PL in the near-IR region (lambda(PL) = 765 nm, phi(PL) = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (phi(PL) < 0.01) is observed. The desorption-sorption response was studied by the solid-state PL spectroscopy. Non-covalent interactions in the crystal including intermolecular H-bonds, CH...pi interactions, and pi...pi stack were found to play decisive roles in the creation of the lamellar architectures, small-molecule trap-and-release behavior, and guest-induced luminescence enhancement.

Automated summary

Two hexanuclear paddlewheel-like clusters with six carboxylic-acid pendants have been isolated in the presence of polar solvent guests. The clusters form alternately stacked lamellar architectures with H-bonded solvent layers. Under UV illumination, the silver cluster displays greenish-yellow photoluminescence while the copper cluster shows photoluminescence in the near-IR region in the solid state.