initiation of fluorescence has also been achieved by encapsulation in metalorganic frameworks. [21] Alternatively, TPE can be substituted in the para-position of the phenyl groups with selected donors which upon coordination to transition metals also lead to rigidification of TPE and initiates fluorescence behavior. [22][23][24][25][26] Recently, an NHC-substituted TPE has been prepared which upon coordination of two M I ions (M = Ag, Au) yields via rigidification an excellent fluorescence emitter in diluted solution (Scheme 1, left). [27] Subsequently various derivatives of NHC-substituted TPE derivatives and their metal complexes have been prepared showing that subtle changes in the structure of the NHC ligand lead to various organometallic architectures with varying photophysical properties. [28][29][30] The heteroaromatic thiophene contains more π-electrons than benzene [31,32] and the tetrathiophenesubstituted ethylene 1,2,3,4-tetrathienylethylene (TTE) has been shown to be a promising AIE emitter in the solid state based on restricted intramolecular rotation (RIM). [31] However, attempts to rigidify the TTE core through complex formation in order to possibly observe fluorescence in solution have not been reported.We have decorated the TTE molecule with four azolium units (imidazolium and benzimidazolium) and prepared the tetrakisazolium salts H 4 -L1(PF 6 ) 4 and H 4 -L2(PF 6 ) 4 (Scheme 1, right). In addition, 2,2′-(2,2-diphenylethene-1,1-diyl)dithiophene (DPDT) was functionalized at the thiophene units with imidazolium units to give the bisimidazolium salt H 2 -L3(PF 6 ) 4 (Scheme 2). The tetrakis-and bisimidazolium salts were subsequently used for the synthesis of a series of dinuclear NHC complexes of composition [M 2 L](PF 6 ) 2 (M = Ag, Au; L = L1, L2) and [M 2 (L3) 2 ](PF 6 ) 2 (M = Ag, Au, Scheme 2). The metal-NHC complexes exhibit the AIE phenomenon and temperaturedependent fluorescence emissions. Molecular structure analyses of the dinuclear tetracarbene complexes indicated that intra-and intermolecular S•••S interactions contributed to the observed red-shift of the emission in the aggregated state. Results and DiscussionThe tetra-NHC precursors H 4 -L(PF 6 ) 4 (L = L1, L2) were prepared following standard procedures. [27,28] The synthesis started Dinuclear silver(I) and gold(I) complexes have been prepared from (NHCthiophene)-substituted ethylene (NHC = N-heterocyclic carbene). Both the 1,2,3,4-tetrathienylethene (TTE)-bridged tetrakisazolium salts (H 4 -L1(PF 6 ) 4 and H 4 -L2(PF 6 ) 4 ) and the 2,2′-(diphenylethene-1,1-diyl)dithiophene (DPDT)bridged bisimidazolium ligand precursors H 4 -L3(PF 6 ) 2 have been prepared and are treated with Ag 2 O to give dinuclear tetracarbene complexes [Ag 2 L] (PF 6 ) 2 (L = L1, L2) and [Ag 2 (L3) 2 ](PF 6 ) 2 , respectively. The silver(I) complexes undergo a transmetalation reaction with [AuCl(THT)] (THT = tetrahydrothiophene) to furnish gold(I) NHC complexes with retention of the original structures. All complexes have been characterized by multi-nuclear magn...
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