Surface Immobilization of a Re(I) Tricarbonyl Phenanthroline Complex to Si(111) through Sonochemical Hydrosilylation

Abstract

A sonochemical-based hydrosilylation method was employed to covalently attach a rhenium tricarbonyl phenanthroline complex to silicon(111). fac-Re(5-(p-Styrene)-phen)(CO)3Cl (5-(p-styrene)-phen = 5-(4-vinylphenyl)-1,10-phenanthroline) was reacted with hydrogen-terminated silicon(111) in an ultrasonic bath to generate a hybrid photoelectrode. Subsequent reaction with 1-hexene enabled functionalization of remaining atop Si sites. Attenuated total reflectance–Fourier transform infrared spectroscopy confirms attachment of the organometallic complex to silicon without degradation of the organometallic core, supporting hydrosilylation as a strategy for installing coordination complexes that retain their molecular integrity. Detection of Re(I) and nitrogen by X-ray photoelectron spectroscopy (XPS) further support immobilization of fac-Re(5-(p-styrene)-phen)(CO)3Cl. Cyclic voltammetry and electrochemical impedance spectroscopy under white light illumination indicate that fac-Re(5-(p-styrene)-phen)(CO)3Cl undergoes two electron reductions. Mott–Schottky analysis indicates that the flat band potential is 239 mV more positive for p-Si(111) co-functionalized with both fac-Re(5-(p-styrene)-phen)(CO)3Cl and 1-hexene than when functionalized with 1-hexene alone. XPS, ultraviolet photoelectron spectroscopy, and Mott–Schottky analysis show that functionalization with fac-Re(5-(p-styrene)-phen)(CO)3Cl and 1-hexene introduces a negative interfacial dipole, facilitating reductive photoelectrochemistry.

Silicon nanocrystal hybrid photocatalysts as models to understand solar fuels producing assemblies

“…This absorption energy is consistent with formation of the singly reduced Re(0) bpy radical anion [Re(bpyc − )(CO) 3 L] n where L is either a bromide ligand (n = −1) or a solvent ligand (n = 0). 12,14,[19][20][21][22][23] This reduced species is a key intermediate in catalytic CO 2 RR activity by Lehn type catalysts and suggests that the surface-bound catalysts exhibit similar behavior to homogeneous catalysts. Notably, the ∼600 and ∼800 nm peaks characteristic of the catalytically inactive Re-Re dimer [43][44][45][46] are not observed (grey trace, Fig.…”

“…Most Si surface functionalization schemes tether catalysts to oxide surface layers, [4][5][6][7][8][9][10] and examples of direct covalent attachment to Si are rare. [11][12][13][14] Understanding the effects of surface immobilization on the catalyst's electrochemical activity as well as its ability to accept photogenerated charges from Si is an essential step in developing a practical PEC system.…”

Statistical Analysis of HAADF-STEM Images to Determine the Surface Coverage and Distribution of Immobilized Molecular Complexes

“…We characterized three different third-row, transition metal-based molecular catalysts immobilized on Si substrates. The CO2 reduction catalysts Re-Bu bpy 26 and Re-Phen 27 , which contain a bipyridine or phenanthroline ligand with a pendant alkene, were covalently attached to hydrogen-terminated Sisubstrates using a thermal hydrosilylation reaction that forms Si-C bonds. 28 The HER catalyst, Pt-Porph, 29,30 which contains carboxylic acid groups on the porphyrin, was immobilized on a TiO2-coated Si substrate through a hydrolysis reaction.…”

“…Re{4-(3-buten-1-yl)4'-methyl-2,2'-bipyridine}(CO)3Cl (Re-Bu bpy), Re(4-(8-nonen-1-yl)-4'-methyl-2,2'bipyridine)(CO)3Cl (Re-Non bpy) and Re(4,4'-bis(3-buten-1-yl)-2,2'-bipyridine)(CO)3Cl (Re-Bu2 bpy) 26 and Re{5-(4-vinylphenyl)1,10-phenanthroline}(CO)3Cl (Re-Phen) 27 were prepared according to literature methods. Et bpy was prepared using a literature procedure, 47 and Re(4-(2-ethen-1-yl)-4'-methyl-2,2'-bipyridine)(CO)3Cl (Re-Et bpy) was prepared using a modified procedure 48…”

Aberration-Corrected STEM to Determine the Surface Coverage and Distribution of Immobilized Molecular Complexes

“…Electrochemistry with functionalized wafers was performed in a N 2 -lled glove box using a previously published electrochemical cell design 44,45 . The back of the functionalized wafer was scratched with a diamond-tipped etching pen to make electrical contact.…”