Self-Assembled Hybrid Bilayers of Palladium Alkanethiolates

Abstract

Octane (C 8 ), dodecane (C 12 ), and hexadecane (C 16 ) thiolates of palladium, as well as their binary mixtures covering the entire range of compositions, have been prepared from organic media and characterized using powder X-ray diffraction (XRD), infrared spectroscopy (FTIR), and scanning tunneling microscopy (STM). All thiolatessmono as well as mixedsadopt bilayered lamellar structures as evidenced by XRD and STM. In monothiolates, the thickness of the bilayer as measured by the d 001 spacing is governed by the length of the alkyl chain, while in hybrid bilayers, the thickness depends on the binary composition as well. In C 8 -C 12 and C 12 -C 16 bilayers, in which the difference in the chain lengths of the constituent thiols is four methylene units, the thickness varies nearly proportionally to the weighted average of the chain lengths. In contrast, the C 8 -C 16 system shows a steplike behavior with only a few compositions (C 8 , 60-80%) exhibiting intermediate d values. The alkyl chains are in all-trans conformation in monothiolates, while in hybrid bilayers, especially in C 12 -C 16 , gauche defects are observed, their concentration being the highest around 50:50 composition. Interestingly, these hybrid thiolates seem to provide adequate free volume to entrap small molecular species.

Gold(I)–Alkanethiolate Nanotubes

“…[16][17][18][19][20][21][22][23][24] The structure of Au(I)-alkanethiolates has also been elucidated; [21][22][23] their repeated bilayer structure is depicted in Figure 1A. Quite surprisingly, the work reported here reveals that the multiple bilayer structure can be curved into tubular forms under prolonged synthetic processes, as shown in Figures 1B-F for our as-prepared Au(I)-SC 12 H 25 nanotubes.…”

“…As reported in Figure 2C, the periodic diffraction peaks reveal that the nearest distance (d 001 ; Fig. 1A) [6,24,26,27] between two adjacent walls is in the range of 3.3840 AE 0.010 nm, depending on the synthetic parameters selected. The straight-chain length of C 12 H 25 SH is about 1.8 nm, which is about half of the observed d 001 -spacing, indicating that some degree of tilting and/or interpenetration of thiolate molecules in the wall structure can be expected.…”

“…In Figure 2A, CÀH vibrations located at 2921 and 2847 cm À1 can be assigned to asymmetric, n as (CH 2 ), and symmetric, n s (CH 2 ), modes, respectively; this FTIR spectrum shows the general fingerprint features of linear alkanethiolates, [22,24,25] which is further confirmed by the absence of the absorption band of n(SÀH) at 2526 cm…”

Highly ordered bilayer structures of gold(I)–alkanethiolates having two types of alkyl groups

“…X-ray diffraction patterns (XRD) were obtained to determine the structure of Au(I)-(SR) x (SR 0 ) y s at room temperature. where longer alkyl groups have four more methylene units, while a step-like variation in the d spacing was observed when the longer alkyl groups had eight more methylene units [7]. This was ascribed to the high disparity in the alkyl chain lengths and the low tendency of the short alkanethiol, such as n-octanethiol in that case, to self-assemble.…”

“…The intrinsic properties of the metal complexes have been known to be strongly dependent on the crystal structure, therefore, many detailed studies have been carried out on the structures of metal complexes, such as silver, copper, and palladium, which are determined mainly by covalent forces [4][5][6][7]. In the case of gold(I) complexes, there are additional non-covalent Au(I)-Au(I) interactions that can also influence the overall properties of the materials [8].…”