The SALSAC approach: comparing the reactivity of solvent-dispersed nanoparticles with nanoparticulate surfaces

Abstract

TiO2 nanoparticles dispersed in solution have been functionalized with metal-binding anchoring ligands and then used to assemble surface-bound heteroleptic copper(i) and iron(ii) complexes. Relative binding preferences were shown through competition.

Are Alkynyl Spacers in Ancillary Ligands in Heteroleptic Bis(diimine)copper(I) Dyes Beneficial for Dye Performance in Dye-Sensitized Solar Cells?

“…The homoleptic compounds [CuL 2 ][PF 6 ] where L = 1-4, were used as a source of copper(I) and ancillary ligand 1-4 to assemble surface-bound heteroleptic dyes [Cu(5)(L)] + using the surfaces-asligands, surfaces-as-complex (SALSAC) ligand exchange methodology [50,51]. The phosphonic acid anchoring ligand 5 (Scheme 2) was selected because of its superior binding to TiO 2 with respect to carboxylic acids [51], and because copper(I) dyes with phosphonic acids or phosphonates [52] with a phenyl spacer between the PO(OH) 2 and bpy units are superior to carboxylic and cyanoacrylic acids in terms of DSC performance and/or ease of synthesis [53][54][55].…”

“…In contrast, anchoring ligand 5 bears a phosphonic acid group. Since we have shown that phosphonic anchoring ligands displace carboxylic anchors in TiO 2 [51], we opted to use n-decylphosphonic acid (DPA, Scheme 6) instead of cheno as the co-adsorbent. Table 3 gives the DSC performance parameters for four DSCs sensitized with [Cu(5)(1)] + in the presence of the co-adsorbent DPA, and the J-V curves for the cells are shown in Figure 12.…”

Schiff Base Ancillary Ligands in Bis(diimine) Copper(I) Dye-Sensitized Solar Cells

“…Heteroleptic [Cu(L anchor )(L ancillary )] + dyes were assembled on commercial FTO/TiO 2 electrodes using the SALSAC ligand-exchange strategy [23,24], as depicted in Scheme 1. The phosphonic acid anchoring ligand 6 (Scheme 6) was chosen because it exhibits enhanced binding to TiO 2 with respect to carboxylic acids [24].…”

“…Heteroleptic [Cu(L anchor )(L ancillary )] + dyes were assembled on commercial FTO/TiO 2 electrodes using the SALSAC ligand-exchange strategy [23,24], as depicted in Scheme 1. The phosphonic acid anchoring ligand 6 (Scheme 6) was chosen because it exhibits enhanced binding to TiO 2 with respect to carboxylic acids [24]. Taking both DSC performance and efficient ligand synthesis into account, we have previously established that copper(I) dyes with phosphonic acid or phosphonate anchors [37] containing a phenylene spacer between the anchor and copper-binding domains are favored over those with carboxylic acid (or carboxylate) and cyanoacrylic acid (or cyanoacrylate) anchors [34,38,39].…”

“…The HETPHEN (HETeroleptic PHENanthroline) approach utilized by Odobel and coworkers [21,22] employs sterically demanding substituents in the 6,6 -positions of a bpy ligand, or in the 2,9-positions of phen, to isolate heteroleptic [Cu(L)(L )][X] complexes and stabilize them with respect to ligand redistribution in solution. In contrast, we have adopted the "surfaces-as-ligands, surfaces-as-complexes" (SALSAC) approach [23,24], which is extremely versatile and allows heteroleptic copper(I) dyes to be assembled directly on a semiconductor surface by ligand exchange between an anchored diimine ligand and a homoleptic copper(I) complex (Scheme 1). A class of ligands that has proven beneficial in bis(diimine)copper(I) dyes is based upon 4,4 -styryl-6,6 -dimethyl-2,2 -bipyridine in which the R group in Scheme 2 is systematically varied.…”