Formation of Molecular Templates Containing Cumulative Double Bonds (CCC) at Organic/Silicon Hybrid Interfaces

Abstract

The cumulative double bond (C=C=C), an important intermediate in synthetic organic chemistry, was successfully prepared via the selective attachment of acetylethyne to Si(111)-7 x 7. The experimental observation of the characteristic vibrational modes and electronic structures of the C=C=C group in the surface species demonstrates the [4 + 2]-like cycloaddition occurring between the terminal O and C atoms of acetylethyne and the neighboring Si adatom-rest atom pair, consistent with the prediction of density functional theory calculations. Scanning tunneling microscopy images further reveal that the molecules selectively bind to the adjacent adatom-rest atom pairs on Si(111)-7 x 7.

p-Benzoquinone on Si(111)-7×7: [6 + 2]-like Cycloaddition

“…With increasing the exposure from 12 to 120 L (Figure c,d), two new peaks at 285.7 and 288.3 eV appear and grow in intensity without saturation, suggesting their physisorption nature. The C 1 (1s) at 288.3 eV can be assigned to two carbonyl C atoms, similar to the value (287.7−289.3 eV) obtained for molecules containing intact carbonyl groups on Si(111) surfaces. , The C 2 (1s) at 285.7 eV is associated with the four ethylenic C atoms. For chemisorbed p -benzoquinone (Figure e), the C 1s spectrum can be deconvoluted into two peaks at 284.9 and 286.4 eV, with an area ratio of ∼2:1.…”

“…Recently, organic modification of silicon surfaces has been attracting continuous attention due to the great opportunities to tailor the surface electronic, optical, and biological properties by exploiting the organic reaction toolbox. – The binding of multifunctional organic molecules – is of particular interest since the intact functional groups may protrude from the surface, providing a molecular template to create more sophisticated and desirable structures. Specifically, considerable effort has been devoted to carbonyl-containing compounds, including simple carbonyls, – dicarbonyls, , and conjugated and unconjugated unsaturated carbonyls. – Reaction competition and selectivity have been discussed , between different binding modes such as O···Si dative bonding, [2+2] CO, [2+2] CC, [4+2] cycloadditions, ene-like reactions, and tetra-σ binding.…”

Chemical manipulation of multifunctional hydrocarbons on silicon surfaces

“…A similar oxygen-containing compound, acetylethyne (HC≡C-C(CH 3 )=O), also undergoes a similar transformation to produce a shorter cumulative double bond chain, -C=C=C-. This reaction was confirmed by exhaustive HREELS, XPS, STM, and DFT investigation [314].…”

Reaction Mechanism and Regioselectivity of Methyl Oxirane on Si(111)-(7 × 7)

“…This cluster includes an adjacent adatom–rest atom pair and serves as the substrate for binding methyl oxirane. Previous studies have proved its success in predicting the adsorption energies, binding configurations, and reaction pathways of organic molecules chemisorbed on Si(111)-(7 × 7). ,− The DFT calculations were performed using the DMol3 − code in Materials Studio. In our calculation, the exchange-correlation potential was incorporated in the generalized gradient approximation (GGA) using the Perdew–Burke–Ernzerhof functional (PBE) .…”

“…Previous work has reported that organic molecules containing one or more unconjugated CC, CO, or CN bonds mainly react with Si(111)-(7 × 7) through the [2 + 2]-like cycloaddition. − When molecules containing conjugated two or more unsaturated bonds such as CC–CC, CC–CO, or CC–CO, the reaction mechanism becomes complicated, and normally, the [4 + 2]-like cycloaddition occurs. ,, Epoxide molecules, which belong to cyclic ether with a three-membered epoxy ring, are widely used in adhesives, paints, and chiral chemical industries, yet their adsorption behaviors on the silicon surfaces are less studied. Ferraz et al theoretically examined the reaction of ethylene oxide with Si(100) and found that C–C bond in the epoxy group breaks and results in a Si–C–O–C-Si ring upon adsorption.…”