Formation of Infinite Chains and Supramolecular Arrays

Small changes in substituents may lead to different aurophilic aggregation patterns. Thus, different structures have been described for very similar species and polymorphs of different nuclearities have even been found for one complex. Thus, a classification based only on the nuclearity of the aggregates is not only difficult, but may also hide other interesting comparisons. For these reasons some chain structures have been mentioned above. The following tries to complete those commentaries. 

Among the widely studied [AuX(PR3)] (X = halogen, PR3 tertiary phosphine) [AuBrL] (L = 2-methylphenylphosphine) crystallizes as a folded chain [65]. Chains of the tetrahydrothiophene and tetrahydroselenophene complexes [AuX(EC4H8)] (E = S, X = Cl, Br or I E = Se, X = I) [66, 67] exhibit different patterns. In the crystal structure of the tetrahydrothiophene compounds [AuX(SC4H8)] (X = Cl, Br) neutral units associate, whereas the structure of the iodine complexes consists of Aul2 and 

The building block [Au(CN)2] has been revealed as a versatile unit in the formation of heteronuclear arrays which, in some cases, display unusual and interesting luminescent properties, such as vapochromic behavior. In many of these complexes the cyanide group uses the carbon and nitrogen ends as Lewis bases able to coordinate two different metal cations (i.e., Au-CN-M) [82-86]. These ideas may be illustrated by the reaction of K[Au(CN)2] with MX2 salts (M = Cu, Ni, Co, Mn  

X = C104, N03...) and pyrazine which affords [M(pyrazine)][Au(CN)2]2 compounds. 

The dimensional patterns or/and properties change upon formation of these heteronuclear derivatives. For example, the structure of the copper derivative consists of a 3D array with chains of Cu(II)-pyrazine units connected by [Au(CN)2] bridges a second identical network connected through aurophilic interactions interpenetrates. 

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