A novel method for creation of free volume in a one-component self-assembled monolayer. Dramatic size effect of para-carborane

Single Component Self‐Assembled Monolayers of Aromatic Azo‐Biphenyl: Influence of the Packing Tightness on the SAM Structure and Light‐Induced Molecular Movements

“…Independent of the free volume available, both compounds show very high yields of photoconversion in SAMs. [22,23,26,28] The yields of photoisomerization of AZO1 and AZO2 in SAMs on Au were found to be close to 100% and comparable within the experimental error. Significantly, this result questions the common believe that isomerization in SAMs of azo-compounds can only be achieved efficiently, when enough free volume is available in the monolayer.…”

“…Significantly, very similar rates of the thermal back reaction have been found for AZO2 SAMs [k ¼ (1.67 AE 0.10) Â 10 À4 s À1 (Au); k ¼ (1.33 AE 0.06) Â 10 À4 s À1 (Pt)] and AZO2 in solution [k ¼ (1.19 AE 0.09) Â 10 À4 s À1 ] suggesting that the switching in the SAMs is not additionally hindered by a lacking free volume [18][19][20][21][22][23][24][25][26]28] and is mostly a property (in the sense of the yield and kinetics) of the individual molecules. This agrees perfectly with a low packing density and orientational order in these films (see below).…”

“…[23,27] Further, bulky subunits have been incorporated into the azo-molecules in an effort to provide enough free volume for the isomerization. [28] Finally, photoisomerization of azo-molecules was found to occur in SAMs on Si(111) taking advantage of the loosely packed character of such films. [29] Only a very limited number of publications reported photoactive molecular films consisting of a single component.…”

Gap-mode SERS studies of azobenzene-containing self-assembled monolayers on Au(111)

“…This is most probably due to the high packing density of these adlayers (e.g. [45]), which prevents trans-cis photoisomerisation of the azobenzene moieties due to steric effects [81][82][83]. The observed illumination effects for 5 SAMs represent the first Raman spectroscopic observation of a photoinduced cis state of an azobenzene-containing self-assembled monolayers on a planar metallic surface.…”

Self-assembly of triazatriangulenium-based functional adlayers on Au(111) surfaces

“…7 This is most commonly accomplished by employing mixed monolayers with short-chain spacer molecules. 5,6,[8][9][10][11][12][13][14][15][16][17] More modern approaches to enforce a sufficient free volume employ specially designed molecules, which feature additional bulky spacer groups 6,[18][19][20][21] or molecular tripods [22][23][24][25] as basis. Nevertheless, these types of adlayers also exhibit intrinsic disadvantages such as a comparable low structural order or lack of temporal stability due to phase separation.…”