A family of cyano-bridged copper(II)-copper(I) mixed-valence polymers containing diamine ligands of formula [Cu(pn)(2)][Cu(2)(CN)(4)] (1, pn = 1,2-propanediamine), [Cu(2)(CN)(3)(dmen)] (2, dmen = N,N-dimethylethylenediamine), and [Cu(3)(CN)(4)(tmen)] (3, tmen = N,N,N',N'-tetramethylethylenediamine) have been prepared with the aim of analyzing how their architecture may be affected by steric constraints imposed by the diamine ligands. In the absence of diamine and with use of the voluminous NEt(4)(+) cation, the copper(I) polymer [NEt(4)][Cu(2)(CN)(3)] (4) forms. The structure of 1 consists of a three-dimensional diamond-related anionic framework host, [Cu(2)(CN)(4)](2-), and enclathrated [Cu(pn)(2)](2+) cations. The structure of 2 is made of neutral corrugated sheets constructed from fused 18-member nonplanar rings, which contain three equivalent copper(I) and three equivalent copper(II) centers bridged by cyanide groups in an alternative form. The 3D structure of 3 consists of interconnected stair-like double chains built from fused 18-member rings, which adopt a chairlike conformation. Each ring is constructed from two distorted trigonal planar Cu(I) centers, two bent seemingly two-coordinated Cu(I) centers, and two pentacoordinated Cu(II) atoms. The structure 4 is made of planar anionic layers [Cu(2)(CN)(3)](n)(n-) lying on mirror planes and NEt(4)(+) cations intercalated between the anionic layers. From the X-ray structural results and calculations based upon DFT theory some conclusions are drawn on the structure-steric factors correlation in these compounds. Compound 1 exhibits very weak luminescence at 77 K with a maximum in the emission spectrum at 520 nm, whereas compound 4 shows an intense luminescence at room temperature with a maximum in the emission spectrum at 371 nm. Polymers 2 and 3 exhibit weak antiferromagnetic magnetic exchange interactions with J = -0.065(3) and -2.739(5) cm(-1), respectively. This behavior have been justified on the basis of the sum of two contributions: one arising from the pure ground-state configuration and the other one from the charge-transfer configuration Cu(I)-CN-Cu(II)-CN-Cu(II) that mixes with the ground-state configuration.

Cyanide-bridged bimetallic systems, prepared from assembling cyanometallates and transition metal complexes building blocks, have been shown to exhibit fascinating structures with interesting magnetic, electrochemical, magneto-optical and zeolitic properties. 1 Linear cyanometallates, [M(CN) 2 ] 2 (M = Ag(I) and Au(I)), however, have been infrequently used as building blocks, probably as a consequence of their diamagnetic nature. Interestingly, gold(I) atoms of dicyanoaurate groups may be involved in intermolecular interactions comparable to hydrogen bonds. This closed-shell intermolecular interaction between gold(I) atoms, sometimes called aurophilicity, is known to be an useful tool for the design of intriguing and interesting polymeric structures in solid state. 2 Therefore, the interplay between covalent and aurophilic interactions involving dicyanoaurate groups might produce novel structural topologies. Moreover, according to precise theoretical calculations, the Au-Au interaction is effective over a wide range of distances. 3 In a earlier statistical study 4 based on 693 goldcontaining structures, it was found that there exists a strong correlation between the Au-Au distance (in the range 3-4 Å) and the dihedral angle between the donor atoms attached to the two adjacent gold atoms: the shorter the Au-Au distance is, the higher will be the probability of the staggered conformation. This has been also observed for dicyanoaurate containing compounds. 5 An interesting cation used in synthetic work with dicyanoaurate(I) anions is the cobalt(II) cation with its ability to display either octahedral or tetrahedral coordination. 6 For both chromophores the resulting structure in the solid state is a threedimensional network, where both ends of the dicyanoaurate(I) anions are coordinated to a cobalt(II) cation. Interestingly, the shortest Au-Au distances are significantly different: 3.11 Å in the tetrahedral and 3.33 Å in the octahedral analogue. If some of the coordination sites of a cation are blocked by an additional ligand, the dimensionality can be varied and then it might be possible to analyse the influence of the aurophilic interactions on the final structure. For instance, in a formally 1D structure of (tmeda)Cu[Au(CN) 2 ] 2 (tmeda = N,N,NA,NA-tetramethylethylenediamine) 7 the aurophilicity enhances the dimensionality to 3D, with Au-Au distances of 3.345 and 3.538 Å, less than the sum of the van der Waals radii of Au (3.60 Å).Here we applied the same strategy in synthetic work. Each cobalt assumes a slightly distorted octahedral CoN 4 O 2 coordination polyhedron, which is made up of four nitrogen atoms from the bridging cyanide groups in plane and two oxygen atoms of the DMF molecules in trans-positions. The Co-N bond distances are in the range 2.086(11) to 2.116(12) Å whereas Co-O bond distances are 2.088(10) and 2.093(10) Å. As expected, the two crystallographically non-equivalent [Au(CN) 2 ] 2 anions are almost linear with C-Au-C bond angles of 177.9(6) and 175.5(6)°. The CN-Co and NC-Au bond angles do n...