A Dynamic Combinatorial Library of Cyclic AuI2NiII Complexes with Cysteine/Penicillamine Showing Solvent-Controlled Crystallization.

A dynamic combinatorial library (DCL) is a set of molecular species existing in equilibrium in solution that can undergo self-assembly via reversible chemical bonds. Here, we report a unique DCL system that shows the independent crystallization of products from solvents with slightly different polarities. The reaction of a 1:1 mixture of [Au2(dppm)(dl-cys)2]2- and [Au2(dppm)(dl-pen)2]2- with Ni2+ in solution gave a DCL containing 10 cyclic AuI2NiII molecules of [Au2Ni(dppm)(dl-cys/dl-pen)2]. Upon crystallization, three kinds of enantiomeric pairs, homoleptic-heterochiral C/A-[Au2Ni(dppm)(d-cys)(l-cys)], homoleptic-homochiral [Au2Ni(dppm)(d-pen)2]/[Au2Ni(dppm)(l-pen)2], and heteroleptic-homochiral [Au2Ni(dppm)(d-cys)(d-pen)]/[Au2Ni(dppm)(l-cys)(l-pen)], were produced from the reaction solutions of MeOH, MeOH/H2O, and EtOH/H2O, respectively. The independent crystallization was explained by a combination of the different hydrogen-bonding interactions of the AuI2NiII molecules in the crystal and the different thermodynamic stabilities of the molecules in solution.

Homoleptic versus heteroleptic trinuclear systems with mixed l-cysteinate and d-penicillaminate regulated by a diphosphine linker.

Controlled generation of homoleptic versus heteroleptic AuI2M (M = NiII, ZnII) trinuclear complexes, which is achieved by a slight change in the diphosphine P^P linker of digold(i) metalloligands, [Au2(P^P)(d-pen)2]2- (L1P^P; d-pen = d-penicillaminate) and [Au2(P^P)(l-cys)2]2- (L2P^P; l-cys = l-cysteinate), is reported. The reactions of a 1 : 1 mixture of L1dppm and L2dppm (dppm = bis(diphenylphosphino)methane) with M = NiII, ZnII gave the homoleptic AuI2M complexes, [M(L1dppm)] and [M(L2dppm)], which co-crystallized to form [M(L1dppm)]·[M(L2dppm)] (1M). Similar reactions using L1dppe and L2dppe (dppe = bis(diphenylphosphino)ethane), instead of L1dppm and L2dppm, led to the selective production and crystallization of the heteroleptic AuI2M complex, [M(L3dppe)] (2M; L3dppe = [Au2(dppe)(l-cys)(d-pen)]2-), accompanied by the scrambling of L1dppe and L2dppe. The homoleptic 1M and the heteroleptic 2M showed different absorption (green versus blue) and emission (yellow versus orange) colours for M = NiII and ZnII, respectively.

Silsesquioxane cages as fluoride sensors.

Pyrene functionalized silsesquioxane cages (PySQ) not only provide significant fluorescence from pyrene-pyrene excimers with a very large Stokes shift (Δλ = 143 nm, 69 930 cm-1) in DMSO but also exhibit fluoride capture results coincidentally with a π-π* fluorescence enhancement. On the other hand, PySQ-F- in THF significantly exhibits π-π* fluorescence quenching and a color change can be observed with the naked eye from light yellow to deep orange by forming a charge-transfer (CT) complex among the pyrenyl rings. Moreover, PySQ selectively captures F- with a response time of <2 min and with a very low detection limit (1.61 ppb), while 19F NMR is used to confirm encapsulation of F- with Δδ = 19 ppm.

Synthesis and isolation of non-chromophore cage-rearranged silsesquioxanes from base-catalyzed reactions.

The nucleophilicity of both ortho- and meta-nitrophenolate anions is strong enough to give substituted products, but their basicity also facilitates cage-rearrangement reactions in polyhedral oligomeric silsesquioxanes (POSS). Anions having a stronger basicity, but weaker nucleophilicity, such as CO32-, gave products only from cage-rearrangement, with the cage expansion products being isolable in multi-gram quantities using conventional column chromatography.