Building Layer-by-Layer a Bis(dithiocarbamato)copper(II) Complex on Au{111} Surfaces

Abstract

A bis(dithiocarbamato)copper(II) complex (CuDTC2) was built on Au{111} surfaces (sheets and electrode beads) using different building blocks in a layer-by-layer (LbL) procedure. The process was followed by AFM and cyclic voltammetry. Initially 4-piperidinemethanethiol, which was synthesized here for the first time, was self-assembled on a gold surface and a highly organized array was obtained. The resulting monolayer was treated with CS2 and NH3 to transform the NH groups of piperidine into dithiocarbamate groups (DTC) with the formation of an amphiphilic ligand (DTCpipS) with thiolate and DTC terminal anionic groups. Two reductive desorption peaks were observed in the cyclic voltammogram of self-assembled DTCpipS, a more intense peak at -0.87 V (thiolate group) and a broader, less intense peak at -0.68 V, corresponding to the desorption of the DTC group bound to the gold surface after the ligand made a approximately 180 degrees flip on the surface. Copper(II) and the morpholyldithiocarbamate anion were associated with self-assembled DTCpipS in order to complete the formation of the CuDTC2 complex on the gold surface. In the voltammogram of the LbL self-assembled CuDTC2 complex the reductive desorption peak at -0.68 V disappeared and one single peak was observed at -0.85 V. This corresponds to the reorientation of all of the DTCpipS dianions in order to coordinate to copper(II) through the DTC groups, leaving the self-assembly only through the thiolate groups. The complete formation of the LbL self-assembled CuDTC2 complex was confirmed by XPS and ToF SIMS, with a detected fragment corresponding to the whole complex.

One step gold (bio)functionalisation based on CS2-amine reaction

“…The very negative reduction potential observed for CS 2 (−0.920 V) regarding the desorption of short thiol derivatives, such as mercaptopropanol (E p = −0.784 V [48]) or mercaptopropionic acid SAM (E = −0.800 V [49]), reveals the great stability of the resonant structure among the sulphur and carbon as the result of a good overlap of the orbitals of the ligand and the gold surface. In the case of the pure dithiocarbamate SAM reductive desorption, there is a shift of the potential towards positive direction most probably due to electron delocalisation between the resonant structure N-C(-S 2 ) which may lead to a weaker surface bond [24]. In fact, the desorption of the monolayer prepared by the surface reaction between gold, CS 2 and hexylmethylamine presents two reduction peaks, one more negative at −0.880 V, most probably associated with a fraction of CS 2 that was adsorbed and did not react with the amine, and the other less negative, at −0.800 V due to dithiocarbamate formation.…”

“…DTCs have been commonly used as chelating ligands in coordination chemistry [22,23], and the formation of bis(dithiocarbamate)copper(II) complex built on Au (1 1 1) surfaces, using a layer-by-layer procedure has been reported [24]. It was also demonstrated that monolayers formed from lithium dioctadecyldithiocarbamate [21] display similar capacitance, thickness, crystallinity and wetability than equivalent alkanethiols, and that dithiocarbamates-gold linkages are not disrupted when SAMs are exposed to alkanethiols [25].…”

A scanning tunneling microscopy investigation of the phases formed by the sulfur adsorption on Au(100) from an alkaline solution of 1,4-piperazine(bis)-dithiocarbamate of potassium

“…Particularly, the sulfur-gold system has been the focus of renewed attention in relation to the formation of self-assembled monolayers (SAMs) from alkane and aromatic thiols [6][7][8][9][10][11], dithiols [6] and dithiocarbamates [12][13][14][15][16][17][18][19][20].…”

Photolithography of dithiocarbamate-anchored monolayers and polymers on gold

“…4 In situ DTC formation has proven useful for anchoring a wide variety of amine-terminated molecules onto Au surfaces, ranging from low-molecular weight species to complex structures capable of biomolecular or supramolecular recognition. 4,5,6,7,8,9,10,11,12, 13,14,15,16,17,18,19 Recently, in situ DTC formation has been extended toward the chemisorptive anchoring of polymeric amines such as polyethyeleneimine (PEI). 20 …”