Surface Coupling of Octaethylporphyrin with Silicon Tetrachloride

Abstract

The surface assembly of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) using silicon tetrachloride as a coupling agent was investigated using atomic force microscopy (AFM). Nanopatterned films of Si-OEP were prepared by protocols of colloidal lithography to evaluate the morphology, thickness, and molecular orientation for samples prepared on Si(111). The natural self-stacking of porphyrins can pose a challenge for molecular patterning. When making films on surfaces, porphyrins will self-associate to form co-planar configurations of random stacks of molecules. There is a tendency for the flat molecules to orient spontaneously in a side-on arrangement that is mediated by physisorption to the substrate as well as by π–π interactions between macrocycles to form a layered arrangement of packed molecules, analogous to a stack of coins. When silicon tetrachloride is introduced to the reaction vessel, the coupling between the surface and porphyrins is mediated through covalent Si–O bonding. For these studies, surface structures of Si-OEP were formed that are connected with a Si–O–Si motif to a silicon atom coordinated to the center of the porphyrin macrocycles. Protocols of colloidal lithography were used as a tool to prepare surface structures and films of Si-OEP to facilitate surface characterizations. Conceptually, by arranging the macrocycles of porphyrins with defined orientation, local AFM surface measurements can be enabled to help address mechanistic questions about how molecules self-assemble and bind to substrates.

Synthesis of Metal Nanoparticles Encapsulated with Skewered Porphyrins Assembled by Siloxane Coupling

“…Previous studies have reported that the planar macrocycles are oriented in a cofacial arrangement to form multilayer films on flat substrates [70,75]. The assembly process to generate porphyrin multilayers was monitored with UV/Vis spectroscopy and the bond length between the stacked aromatic ring was investigated with X-ray diffraction studies, as reported by Lee et al [75].…”

“…The orientation of porphyrins on surfaces is determined by factors such as the nature of the peripheral substituents and their position on the macrocycle. The strategy of preparing a coplanar, skewered arrangement of OEP multilayers that are mediated by covalent Si-O bonds has been previously described [70]. Herein, we present results for linking porphyrins with Si-O-Si bridges to metal nanoparticles.…”

Nonlinear optical properties of porphyrin-modified carbon dots composites

“…In recent years, with the wide application of high-power lasers, nonlinear optical (NLO) materials have received significant attention as they can protect the human eyes and sensors from high-power lasers. Among numerous NLO materials, porphyrin (Por) has been widely investigated due to its unique 18 π electron conjugated structure [1], good thermal stability and narrow bandgap [2]. It is reported that modifying porphyrins with carbon nanomaterials could form nanohybrids and enhance NLO properties by synergic effect [3,4].…”