SYNTHESES, STRUCTURES, AND SPECTROSCOPIC PROPERTIES OF GOLD(I) COMPLEXES OF 1,3,5-TRIAZA-7-PHOSPHAADAMANTANE (TPA) - CORRELATION OF THE SUPRAMOLECULAR AU...AU INTERACTION AND PHOTOLUMINESCENCE FOR THE SPECIES (TPA)AUCL AND [(TPA-HCL)AUCL]

The reaction of the cage-type ligand 1,3,5-triaza-7-phosphaadamantane (TPA) with(dimethyl sulfide)gold(I chloride in a molar ratio 1:1 in ap rotic polar solvents affords the complex (TPA)AuCl, 1,in high yield. S imilarly, reacting the protonated TPA ligand in MeOH/CH3CN (2:1) with (tetrahydrothiophene)AuCl gives the protonated product (TPA-HCl)AuCl, 1P, in excellent yield. The cation of 1P becomes deprotonated above ab out pH 4.5. The structures and temperature-dependent photoluminescence properties of 1 and 1P have been determined. Protonation of the TPA l igand remarkably lengthens the solid state, auriophilic Au...Au intera ction in 1P, where the Au...Au separation is 3.322(1) Angstrom, compar ed with 3.092(1) Angstrom in 1. The luminescence spectra of the-two co mpounds are substantially different, clearly a consequence of the chan ge in the Au Au separation associated with the ''supramolecular'' auri ophilic dimerization. While the Cl-Au-P angles are nearly linear in bo th compounds, 177.4 (1) and 175.8 (1)degrees, respectively, a ''crosse d'' dimerization (dihedral angle P-Au-Au'-P' about 105 degrees) occurs . The small cone angle of the TPA ligand allows this Au Au interaction to occur, a dimerization absent for many other tertiary phosphine com plexes of LAuX which have been structurally characterized to date. At 78 K compound 1P luminesces yellow (596 nm), while compound 1 luminesc es intensely red (674 nm). The emission band of 1 is red-shifted by ab out 2000 cm(-1) when compared to that of 1P. The emission bands in bot h compounds blue-shift as the temperature is increased. Between 78 and 298 K the emission band of 1P blue-shifts by about 400 cm(-1) and tha t of 1 by 700 cm(-1). Neither complex-is luminescent in solution. A so lution absorption band has been observed at energies >40000 cm(-1) (24 2 nm). The interpretation of the changes in the low-energy visible emi ssion in the solid state upon changing the auriophilic Au...Au contact is supported by extended Huckel MO calculations wherein, upon shorten ing the Au...Au separation, the HOMO (sigma(u)) orbital is destabilize d, causing a decrease in the KOMO-LUMO gap. (TPA)AuCl is readily conve rted into the corresponding bromide; 2, or iodide, 3, by treating it w ith HBr(aq) or KI. in acetone, respectively. The complex (TPA)AuCH3, 4 , is obtained from (TPA)AuCl and equimolar quantities of MeLi in dieth yl ether. An N-methylated complex [(TPAMe)AuCl]-OSO2CF3, 5, is formed in the reaction of (TPA)AuCl with CF(3)SO(3)Me in dichloromethane. Cry stal data: (TPA-HCl)AuCl.0.5H(2)O, 1P.0.5H(2)O, monoclinic, space grou p C2/e with a = 15.060(2) Angstrom, b = 12.663(2) Angstrom, c = 13.775 (3) Angstrom, beta = 120.60(2)degrees, V = 2261.0(6) Angstrom(3), Z = 8, R = 0.0317 (R(w) = 0.0415); (TPA)AuCl. CH3CN, 1.CH3-CN, orthorhombi c, space group Pbcn, with a = 14.334(2) Angstrom, b = 13.924(3) Angstr om, c = 11.776(2) Angstrom, V = 2350.3 Angstrom(3), Z = 8, R = 0.038 ( R, = 0.0467); (TPA)AuBrCH3CN, 2.CH3CN, orthorhombic, space group Pbcn, a = 14.546-(3) Angstrom, b = 14.138(3) Angstrom, c = 11.898(3) Angstr om, V = 2431.9(9) Angstrom, Z = 8, R = 0.544 (R(w) = 0.075).