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

Abstract

Two hexanuclear paddlewheel-like clusters appending six carboxylic-acid pendants have been isolated with the inclusion of polar solvent guests: [Cu6(Hmna)6]·7DMF (1·7DMF) and [Ag6(Hmna)6]·8DMSO (2·8DMSO), where H2mna = 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 1·7DMF and 2·8DMSO 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 (λex = 365 nm), the solvated hexasilver(I) cluster 2·8DMSO gives intense greenish-yellow photoluminescence in the solid state (λPL = 545 nm, ΦPL = 0.17 at 298 K), whereas the solvated hexacopper(I) cluster 1·7DMF displays PL in the near-IR region (λPL = 765 nm, ΦPL = 0.38 at 298 K). Upon complete desolvation, a substantial bleach in the PL intensity (ΦPL < 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⋯π interactions, and π⋯π 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.

A PN(Pz)P ligand protected Au2Cu2complex for photoluminescent ultra-low humidity detection with reversible single-crystal-to-single-crystal transformations

“…In recent years, many photoluminescent Au/Ag/Cu complexes have been employed for the reversible detection of organic vapours such as MeOH, [6][7][8][9][10] MeCN, [11][12][13] THF, 14,15 DMSO, [16][17][18] and CH 2 Cl 2 , [19][20][21][22] as well as small inorganic molecules including H 2 , 23 O 2 , [24][25][26][27][28] CO, NO 29 and H 2 O 8,30 with good sensitivity, selectivity, reproducibility and portability. The chromic photoluminescent responses of these complexes are attributed to their weak interactions with target molecules, via H-bonding, [31][32][33] C-H⋯π 9,34,35 and π⋯π interactions, [36][37][38] molecular deformation or formation/disruption of metal-solvent bonds. 7,[39][40][41][42] For example, Yam and co-workers have reported that the green emission of the cluster [Au 10 {μ-Ph 2 PN(-CH 2 -o-Py)PPh 2 } 4 (μ 3 -S) 4 ](PF 6 ) 2 shifted to blue and red when exposed to CH 2 Cl 2 and MeOH vapours, respectively, due to the changing of crystal forms.…”