Photoacid Generating Ligands for Development of Positive-Tone Directly Photopatternable Metal Complexes

Abstract

Photoacid generating ligands, 4-(2-nitrobenzy-loxycarbonyl)catechol and 4-(6-nitroveratryloxycarbonyl)catechol, and indium tin and titanium complexes thereof, were synthesized. These metal complexes perform as positive-tone, directly photopatternable indium tin oxide (ITO) or titanium oxide film precursors. After exposure, acid-bearing selectively soluble complexes could be removed to give patterned films upon developing in aqueous base, which were transformable to the corresponding pattern-preserving metal oxide film. Micropatterning of ITO and titanium oxide films was accomplished with the photoreactivity of the 2-nitrobenzyloxycarbonyl (NBOC) and 6-nitroveratryloxycarbonyl (NVOC) moiety bearing ligands.

Simultaneous Direct Formation of Fine Copper Mesh Transparent Electrodes on Both Sides of Glass Substrate Using Wavelength Selective Photoreactive Niobium Complexes

“…16) However, similar to the reported indium analogues, high contrast patterning was achieved with use of one molar equivalent or less of the nitrobenzyl ester ligand as opposed to the two equivalents required for photopatterning titanium. Accordingly, absorbance due to ligand-metal charge transfer (LMCT) was less intense than the titanium analogues 16) as can be observed in Fig. 2.…”

A solution process for preparation of low resistance layered indium tin oxide films

“…6. Broadening of the ligand NMR signals for indium complexes due to dissociation-reformation of In-O bonds has been observed [21], therefore, sharpening of the ligand signals may be due to stronger In-O bonding. This may be a result of nitrate base influence on the electronic character of indium resulting in higher affinity towards the ligand in the nitrate base complex.…”

“…(iii) Optionally anneal the ITO film in a reducing atmosphere to give oxygen-deficient ITO with increased carrier mobility allowing a decrease in resistance and adjustment of optical properties. Photo-patternable nitrobenzyl 3,4-dihydroxybenzoate complexes were found to transform to metal oxide by anisotropic contraction along the axis perpendicular to the substrate plane to give void and crack free films [21], a phenomenon we believe the flat ligand to be responsible for. In a proceeding paper [22], increase of the heating rate for pyrolysis from 10 to 25°C/min was found to significantly decrease the ITO resistivity inspiring further investigation of application of 3,4-dihydroxybenzoate complexes (Fig.…”

“…% ITO~100 nm particle dispersion in 2-propanol (ITO-np) was used as purchased from Aldrich. Indium tin complexes of ethyl 3,4-dihydroxybenzoate (1) [22], and photosensitive 6-nitroveratryl 3,4-dihydroxybenzoate (2) [21] (Fig. 2) and 0.5 mol/L solutions thereof in ethyl lactate/γ-butyrolactone/N,N-dimethylacetamide were prepared according to the procedure previously reported.…”

“…Catechol-indium complexes appear in the literature, usually related to structural studies or in application of 111 In in radio-pharmacology [19,20], however, we have yet to come across application of catecholindium tin complexes for ITO film formation by solution deposition prior to the work done on complexes that could be photo-patterned [21]. Our attraction to catechol as a ligand originates from the flat structure and minimal volume compared to other more simple ligands like triethanolamine or acetylacetonate that protrude in three dimensions.…”