Structure, solution assembly, and electroconductivity of nanosized argento-organic-cluster/framework templated by chromate.

In view of elucidating potential structures and assembly mechanism of silver clusters and silver cluster-based metal-organic frameworks, we prepared four argento-organic-clusters/frameworks where the structures were directed by chromate in the presence of different thiolates. All four structures with t BuC6 H4 S- , Si Bu- , and Si Pr- consist of three core-shells, an inner CrO4 2- , an intermediate Ag-S aggregate and finally the protective organic moieties. {(HNEt3 )3 [Ag(CrO4 )4 @Ag46 (SC6 H4 t Bu)24 (CF3 COO)18 (DMF)4 ]} (1) is a supertetrahedron with an inner Ag(CrO4 )4 tetrahedron shelled by four fused Ag11.5 S6 lobes. [(CrO4 )5 @Ag40 (Si Bu)27 (CF3 COO)3 ]n (2) is an undulated snake-like tube housing the infinite CrO4 2- tetrahedra. [(CrO4 )2 @Ag41 (Si Bu)30 (NO3 )3 (CN)4 ]n (3) forms an uncommon 7-connected kwh network incorporating hexagonal layers of Ag19 (Si Bu)15 balls with a single inner CrO4 2- connected by another Ag atom. Both enantiomeric chiral qtz frameworks of [CrO4 @Ag20 (Si Pr)10 (Cr2 O7 )2 (COOCF3 )4 (DMF)4 ]n (4) were structurally characterized. In 4, Cr2 O7 2- connects the Ag20 (Si Pr)10 clusters with a trapped CrO4 2- into a 3D quartz (qtz) structure, where the spherical cluster acts like oxygen and Cr2 O7 2- takes the place of Si in SiO2 . Electrospray ionization mass spectrometry (ESI-MS) analysis of the reaction solutions of 1-4 clearly indicated that (i) the Ag(CrO4 )4 @Ag46 core of 1 can retain its molecular structure in the solution and (ii) the chromate-templated polynuclear silver-thiolate species in solution are important building blocks to construct the 1D or 3D motif for 2-4. The electrochemistry in sulfuric acid and enhancement of the electrical conductivity upon I2 doping have also been reported.