Odd-even effects in aryl-substituted alkanethiolate SAMs: nonsymmetrical attachment of aryl unit and its impact on the SAM structure
Aryl-substituted alkanethiolate (AT) self-assembled monolayers (SAMs) exhibit typically so-called odd-even effects, viz. systematic variations in the film structure, packing density, and molecular inclination depending on the parity of the number of the methylene units in the alkyl linker, n . As an...
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Published in | Physical chemistry chemical physics : PCCP Vol. 26; no. 9; pp. 7563 - 7572 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
England
Royal Society of Chemistry
28.02.2024
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Subjects | |
Online Access | Get full text |
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Summary: | Aryl-substituted alkanethiolate (AT) self-assembled monolayers (SAMs) exhibit typically so-called odd-even effects,
viz.
systematic variations in the film structure, packing density, and molecular inclination depending on the parity of the number of the methylene units in the alkyl linker,
n
. As an exception to this rule, ATs carrying an anthracen-2-yl group (Ant-
n
) as tail group were reported to have different behavior due the non-symmetric attachment of the anthracene unit to the AT linker, providing additional degree of freedom for the molecular organization and allowing for partial compensation of the odd-even effects. In this context, the structure of SAMs formed by adsorption of anthracene-substituted ATs (Ant-
n
;
n
= 1-6) at room temperature on Au(111) substrate was investigated by high-resolution scanning tunnelling microscopy (STM). Most of these SAMs exhibit a coexistence of two different ordered phases, some of which are common for either
n
= odd or
n
= even while other vary over the series, showing a broad variety of different structures. The average packing density of the Ant-
n
SAMs, derived from the analysis of the STM data, varies by 7.5-10% depending on the parity of
n
, being, as expected, higher for
n
= odd. The respective extent of the odd-even effects is noticeably lower than that usually observed for other aryl-substituted monolayers (∼25%), which goes in line with the previous findings and emphasizes the impact of the non-symmetric attachment of the aromatic unit.
Due to non-symmetric attachment of the anthracene unit to the alkanethiolate linker, the respective monolayers on Au(111) exhibit low extent of the odd-even effects and distinct polymorphism, showing, at the same time, high structural order. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1463-9076 1463-9084 |
DOI: | 10.1039/d4cp00311j |