No abstract

A synthetic strategy has been developed to prepare cyclotriphosphazenes that bear polycatenar aromatic esters as promesogenic units linked to phosphorus atoms. The microsegregation of the rigid and flexible parts of the system and the space-filling properties are the driving forces that determine the kind of mesomorphism exhibited by the organocyclotriphosphazenes. Mesogenic units that contain only one terminal alkyl chain give rise to calamitic mesomorphism, since the molecules are arranged to give a cylindrical superstructure with the aromatic promesogenic cores elongated in a manner approximately perpendicular to the cyclotriphosphazene ring. On the other hand, mesogenic units that contain three long terminal chains exhibit columnar mesophases. In this case, a discotic structure consisting of promesogenic cores arranged approximately parallel to the cyclotriphosphazene ring can explain the columnar organization. The X-ray diffraction patterns corresponding to the Col(h) mesophase of the cyclotriphosphazene with dodecyloxy chains (8) indicate the presence of helical ordering, which was confirmed for a homologous compound bearing stereogenic centers on two of the terminal chains (11). All of the synthesized phosphazenes show a high thermal stability.

The aurophilic attraction or aurophilia is an empirically found phenomenon consisting of a weak attractive force between gold atoms that is, nevertheless, as strong as hydrogen bonds. This phenomenon produces, inter alia, shorter intramolecular and intermolecular distances than expected between gold centers and unexpected geometries.

Piperidinium 9H-fluorene-9-carbodithioate and its 2,7-di-tert-butyl-substituted analogue [(pipH)(S(2)CCH(C(12)H(6)R(2)-2,7)), R = H (1a), t-Bu (1b)] and 2,7-bis(octyloxy)-9H-fluorene-9-carbodithioic acid [HS(2)CCH(C(12)H(6)(OC(8)H(17))(2)-2,7), 2] and its tautomer [2,7-bis(octyloxy)fluoren-9-ylidene]methanedithiol [(HS)(2)C=C(C(12)H(6)(OC(8)H(17))(2)-2,7), 3] were employed for the preparation of gold complexes with the (fluoren-9-ylidene)methanedithiolato ligand and its substituted analogues. The gold(I) compounds Q(2)[Au(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)], where Q(+) = PPN(+) or Pr(4)N(+) for R = H (Q(2)4a) or Q(+) = Pr(4)N(+) for R = OC(8)H(17) [(Pr(4)N)(2)4c], were synthesized by reacting Q[AuCl(2)] with 1a or 2 (1:1) and excess piperidine or diethylamine. Complexes of the type [(Au(PR'3))(2)(mu-kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with R = H and R' = Me (5a), Et (5b), Ph (5c), and Cy (5d) or R = t-Bu and R' = Me (5e), Et (5f), Ph (5g), and Cy (5h) were obtained by reacting [AuCl(PR'(3))] with 1a,b (1:2) and piperidine. The reactions of 1a,b or 2 with Q[AuCl(4)] (2:1) and piperidine or diethylamine gave Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)] with Q(+) = PPN(+) for R = H [(PPN)6a], Q(+) = PPN(+) or Bu(4)N(+) for R = t-Bu (Q6b), and Q(+) = Bu(4)N(+) for R = OC(8)H(17) [(Bu(4)N)6c]. Complexes Q6a-c reacted with excess triflic acid to give [Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(kappa(2)-S,S-S(2)CCH(C(12)H(6)R(2)-2,7))] [R = H (7a), t-Bu (7b), OC(8)H(17) (7c)]. By reaction of (Bu(4)N)6b with PhICl(2) (1:1) the complex Bu(4)N[AuCl(2)(kappa(2)-S,S-S(2)C=C(C(12)H(6)(t-Bu)(2)-2,7))] [(Bu(4)N)8b] was obtained. The dithioato complexes [Au(SC(S)CH(C(12)H(8)))(PCy(3))] (9) and [Au(n)(S(2)CCH(C(12)H(8)))(n)] (10) were obtained from the reactions of 1a with [AuCl(PCy(3))] or [AuCl(SMe(2))], respectively (1:1), in the absence of a base. Charge-transfer adducts of general composition Q[Au(kappa(2)-S,S-S(2)C=C(C(12)H(6)R(2)-2,7))(2)].1.5TCNQ.xCH(2)Cl(2) [Q(+) = PPN(+), R = H, x = 0 (11a); Q(+) = PPN(+), R = t-Bu, x = 2 (11b); Q(+) = Bu(4)N(+), R = OC(8)H(17), x = 0 (11c)] were obtained from Q6a-c and TCNQ (1:2). The crystal structures of 5c.THF, 5e.(2)/(3)CH(2)Cl(2), 5g.CH(2)Cl(2), (PPN)6a.2Me(2)CO, and 11b were solved by X-ray diffraction studies. All the gold(I) complexes here described are photoluminescent at 77 K, and their emissions can be generally ascribed to LMMCT (Q(2)4a,c, 5a-h, 10) or LMCT (9) excited states.

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.