Carboxylic acid anchoring groups

M. Carrara, F. Nuesch, L Zuppiroli, Carboxylic acid anchoring groups for the constraction of self-assembled monolayers on organic device electrodes, Synth. Metals... 

With carboxylic acid anchoring groups, it is not too difficult and they can be connected to a variety of functionalities through simple hydrocarbon chains. The principal limitation is with groups that would themselves react with the acid. The amino-functionality is a prime example of this. 

Typical nucleophilically cleavable linkers are the REM resin linker 86 [75] (polymer-bound benzyl acrylate regenerated Michael acceptor) and the Dde group 87 (ADCC (4-Acetyl-3,5-dioxo-l-methylcyclohexane carboxylic acid) anchor) [76], which are linkers for tertiary and primary amines, respectively (Figure 6.1.7). 

In the preparation of a combinatorial library of a,[3-unsaturated carboxylic acids, a group from Rhone Poulenc Rorer utilized the H WE-olefination reaction. Starting from 1-substituted phosphonoacetic acid anchored to polystyrene, a 48-membered library containing a diverse set of aldehydes (aliphatic, aromatic and basic) was produced, with an (E/Z)-ratio that was highly dependant on the a-substituent of the phosphonate, where hydrogen gave a 9 1 ratio in favor of the (Ej-product... 

Chen, F., Li, X., Hihath, J., Huang, Z. and Tao, N. (2006) Effect of Anchoring Groups on Single-Molecule Conductance Comparative Study of Thiol-, Amine-, and Carboxylic-Acid-Terminated Molecules. Journal of the American Chemical Society, 128, 15874-15881. 

Cleavage of all the linkers described above provide a functional group (carboxylic acid, amide, amine, etc) at the anchoring position. Silyl-based handles 71,72, and 73 as well as germanium-based handle 74 insert a C-H bond at the anchoring position and are referred to as traceless (Fig. 15) [82-... 

Several zinc(II) and aluminum(III) phthalocyanine derivatives substituted with carboxylic acid and sulfonic acid groups were anchored to nanocrystalline Ti02 films and tested for their photovoltaic behavior.72,73 Interestingly, zinc(II)-2,9,16,23-tetracarboxyphthalocyanine (55) exhibited 45% monochromatic current conversion efficiency at 700 nm. It is shown that electron injection to Ti02 occurs from the excited singlet state of the phthalocyanine derivatives. The... 

Chen F, Li X, Hihath J, Huang Z, Tao N (2006) Effect of anchoring groups on singlemolecule conductance comparative study of thiol-, amine-, and carboxylic-acid-terminated molecules. J Am Chem Soc 128 15874—15881... 

Chemical treatments, such as strong oxidising acid mixtures of HN03/H2S04 under sonication, modify CNT surfaces with anchor groups, including carboxylic, carbonyl and hydroxyl functions, eventually used to covalently connect molecules to the tubes. The carboxylic acid groups are often the most common... 

The most common linker molecules are pyrene derivatives, which have been used, for example, to link Au [64,65] and Pd [66] NPs, as well as QDs [67] to CNTs. Martin et al. chemically attached a n-extended tetrathiafulvalene (exTFF) group to pyrene prior to n-n hybridization on SWCNTs in order to investigate donor-acceptor interactions between the SWCNT and electron rich exTFF [68], More recently, the same group has synthesized a complex molecule consisting of two exTFF anchors connected via a flexible linkage that also consists of a second generation carboxylic terminated den-dron [69]. Here, n interactions between the exTFF anchors and the SWCNTs lead to hybridization while the carboxylic acid groups of the dendron (when de-protonated) lead to increased solubility in aqueous solutions [69]. 

This strategy consists in the initial modification of the silica surface with organosilanes having suitable anchoring groups, which are either reactive themselves or can be additionally activated for the final attachment of the chiral selector. The choice of the proper silane will depend on the presence of suitable functional groups on the chiral entity to be fixed to the matrix. As macrocyclic antibiotics contain hydroxyl, amine, and carboxylic acid functionalities, they can be linked to the silica surface in a variety of different ways [7, 55]. The obvious drawback of the stepwise assemblage of chiral selectors on the silica surface is the eventual formation of additional polar or ionizable sites on the matrix, which may cause unselective retention of chiral analytes. 

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