Syntheses, Structure, and Photoluminescence Properties of the 1-Dimensional Chain Compounds [(TPA)₂Au][Au(CN)₂] and (TPA)AuCl (TPA = 1,3,5-Triaza-7-phosphaadamantane)

Abstract

The structures and temperature-dependent photoluminescence properties of the one-dimensional compounds [(TPA)(2)Au][Au(CN)(2)], 1, and (TPA)AuCl, 2, are reported. An extended linear chain with weak Au.Au interactions along the c-axis is evident in the structure of 1, and a helical chain with a pitch of 3.271 A is seen for 2. The intrachain Au...Au separation is 3.457(1) and 3.396(2) A in 1 and 2, respectively. As a result of this weak Au...Au interaction, the physical properties of these compounds are anisotropic. Scanning electron microscopy (SEM) studies indicate that single crystals of both compounds are noninsulating. Single crystals of 1 do not luminesce visibly, but grinding the crystals finely initiates a strong green emission under UV irradiation at room temperature. Further interesting optical properties include the dependence of the emission profile of the powder on the exciting wavelength and luminescence thermochromism. When excited at wavelengths < 360 nm, the powder exhibits a blue emission at 425 nm while excitation with longer wavelengths leads to a green emission near 500 nm. While the green emission dominates at ambient temperature, cooling to cryogenic temperatures leads to the dominance of the blue emission. Fibers of 2 are luminescent at 78 K with an emission band centered at 580 nm. Compound 1 crystallizes in the orthorhombic space group Cccm (No. 66), with Z = 2, a = 6.011(1) A, b = 23.877(6) A, c = 6.914(1) A, V = 992.3(3) A(3), and R = 0.0337. Compound 2 crystallizes in the trigonal space group R3 (No. 148), with Z = 18, a = 22.587(2) A, b = 22.587(2) A, c = 9.814(2) A, V = 4336 A(3), and R = 0.0283.

Polymorphism and luminescent behavior of linear, two-coordinate gold(i) complexes

“…[Au I (CN)2] are normally non-luminescent, but they become photoluminescent after grinding (9). Similarly, a gold(I) thiouracilate complex also becomes luminescent when subject to mild pressure.…”

Cyanide-bridged bimetallic multidimensional structures derived from organotin(IV) and dicyanoaurate building blocks: ion exchange, luminescence, and gas sorption properties

“…The separation between the gold atoms in K[Au(CN) 2 ] is 3.64 Å [37,42], which is longer than those found in 1. The emission peak at 390 nm in K[Au(CN) 2 ] has been attributed to this weak aurophilic interaction between the dicyanoaurate units [42].…”

“…The importance of the aurophilic interactions in influencing the luminescence properties of gold(I) compound is now well recognized [37]. The Au-Au bond distance in complexes showing aurophilic interactions ranges from 2.70 to 3.50 Å [38][39][40][41], and owing to this interaction, the gold(I) complexes are potentially luminescent.…”

Water-soluble and water-stable Gold(I), Gold(II) and Gold(III) phosphine complexes: The early years

“…The complexes [AuX(TPA)]·CH 3 CN (X = Cl, Br) form dimers with short Au ... Au contacts in the solid state, in contrast, unsolvated [AuCl(TPA)] is a chain polymer in the solid-state [13]. The coordinated TPA ligand can be protonated by acid to give the water-soluble derivative [AuCl(TPA-HCl)], which also forms dimers in the solid state.…”