Bottom-up nanotechnology has to start with the precise positioning of molecules. For this purpose we are developing molecular printboards, that is, self-assembled monolayers (SAMs) of molecules that have specific recognition sites, for example, molecular cavities, to which molecules can be anchored through specific and directional supramolecular interactions.[1] Such molecular printboards are prepared by the self-assembly of b-cyclodextrin (b-CD) derivatives on gold and silicon oxide surfaces. Herein we describe how to print or write, by microcontact printing (mCP) and dip-pen nanolithography (DPN), respectively, molecular patterns of guest-functionalized calixarene molecules, dendritic wedges labeled by fluorescent groups, and dendrimers on b-CDterminated printboards. The binding, as well as the desorption of the molecules, can be fine-tuned by chemical design, which allows virtually unlimited flexibility in the chemical functions that can be employed. These structures can be subsequently used to direct the adsorption of different materials, for example, fluorescent dyes.Microcontact printing has been developed by Whitesides for the preparation of patterns of molecules on bare surfaces by, for example, the transfer of thiols to gold substrates in the contact areas between a soft polymeric stamp and the substrate. [2,3] This has recently been extended by Mirkin and co-workers to writing with molecules on such surfaces by using the DPN approach.[4] Various types of molecules were deposited onto different substrates by DPN which led to arrays of, for example, DNA, [5] proteins, [6] and nanoparticles. [7] Registry capabilities have been demonstrated as well, [8] and a multipen nanoplotter able to produce parallel patterns with different ink molecules has been developed.[9]b-CD (1 a, Scheme 1) can act as a host for the binding of a variety of small, organic guest functionalities in water through hydrophobic interactions. We prepared self-assembled monolayers (SAMs) of a b-CD heptathioether adsorbate 1 b (Scheme 1) on gold as described before. [10,11] Such adsorbates form densely packed, well-ordered SAMs with equivalent

Three compounds bearing multiple adamantyl guest moieties and a fluorescent dye have been synthesized for the supramolecular patterning of beta-cyclodextrin (CD) host monolayers on silicon oxide using microcontact printing and dip-pen nanolithography. Patterns created on monolayers on glass were viewed by laser scanning confocal microscopy. Semi-quantitative analysis of the patterns showed that with microcontact printing approximately a single monolayer of guest molecules is transferred. Exposure to different rinsing procedures showed the stability of the patterns to be governed by specific supramolecular multivalent interactions. Patterns of the guest molecules created at CD monolayers were stable towards thorough rinsing with water, whereas similar patterns created on poly(ethylene glycol) (PEG) reference monolayers were instantly removed. The patterns on CD monolayers displayed long-term stability when stored under N(2), whereas patterns at PEG monolayers faded within a few weeks due to the diffusion of fluorescent molecules across the surface. Assemblies at CD monolayers could be mostly removed by rinsing with a concentrated CD solution, demonstrating the reversibility of the methodology. Patterns consisting of different guest molecules were produced by microcontact printing of one guest molecule and specific adsorption of a second guest molecule from solution to non-contacted areas, giving well-defined alternating assemblies. Fluorescent features of sub-micrometer dimensions were written using supramolecular dip-pen nanolithography.

Bottom-up nanotechnology has to start with the precise positioning of molecules. For this purpose we are developing molecular printboards, that is, self-assembled monolayers (SAMs) of molecules that have specific recognition sites, for example, molecular cavities, to which molecules can be anchored through specific and directional supramolecular interactions.[1] Such molecular printboards are prepared by the self-assembly of b-cyclodextrin (b-CD) derivatives on gold and silicon oxide surfaces. Herein we describe how to print or write, by microcontact printing (mCP) and dip-pen nanolithography (DPN), respectively, molecular patterns of guest-functionalized calixarene molecules, dendritic wedges labeled by fluorescent groups, and dendrimers on b-CDterminated printboards. The binding, as well as the desorption of the molecules, can be fine-tuned by chemical design, which allows virtually unlimited flexibility in the chemical functions that can be employed. These structures can be subsequently used to direct the adsorption of different materials, for example, fluorescent dyes.Microcontact printing has been developed by Whitesides for the preparation of patterns of molecules on bare surfaces by, for example, the transfer of thiols to gold substrates in the contact areas between a soft polymeric stamp and the substrate. [2,3] This has recently been extended by Mirkin and co-workers to writing with molecules on such surfaces by using the DPN approach.[4] Various types of molecules were deposited onto different substrates by DPN which led to arrays of, for example, DNA, [5] proteins, [6] and nanoparticles. [7] Registry capabilities have been demonstrated as well, [8] and a multipen nanoplotter able to produce parallel patterns with different ink molecules has been developed.[9]b-CD (1 a, Scheme 1) can act as a host for the binding of a variety of small, organic guest functionalities in water through hydrophobic interactions. We prepared self-assembled monolayers (SAMs) of a b-CD heptathioether adsorbate 1 b (Scheme 1) on gold as described before. [10,11] Such adsorbates form densely packed, well-ordered SAMs with equivalent

The 226Ra2+ selectivity of the ionizable (thia)calix[4]crowns 1-4 was determined in the presence of a large excess of the most common alkali and alkaline earth cations. Selective 226Ra2+ (2.9 x 10(-)(8) M) extraction occurs even at extremely high M(n+)/226Ra2+ ratios of 3.5 x 10(7) [M(n+) = Na+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+ (1M)] and an ionophore concentration of 10(-4) M. The selectivity coefficients log(K(Ra)(ex)/K(M)(ex)) are approximately 3.5 for Mg2+, Ca2+, and Sr2+. In the presence of Ba2+, which has very similar chemical properties, only the thiacalix[4]crown-6 derivative 4 showed a selectivity for 226Ra2+. In addition to the remarkable 226Ra2+ selectivities, the effective pH range (pH 8-13) of the thiacalix[4]crown dicarboxylic acids (3 and 4) allows for full regeneration of the ionophores at lower pH values (pH <6).

Bridging of p-tert-butylthiacalix[4]arene afforded 1,3-dihydroxythiacalix[4]arene-monocrown-5 (3b), 1,2-alternate thiacalix[4]arene-biscrown-4 and -5 (4a,b), and 1,3-alternate thiacalix[4]arene-biscrown-5 and -6 (5a,b), depending on the metal carbonates and oligoethylene glycol ditosylates used. Starting from 1,3-dialkylated thiacalix[4]arenes, the corresponding bridging reaction gave 1,3-alternate, partial-cone, and cone conformers 10-19, depending on the substituents present. Temperature-dependent studies revealed that the conformationally flexible 1,3-dimethoxythiacalix[4]arene-crowns 10a-c exclusively occupy the 1,3-alternate conformation. Demethylation exclusively gave the cone 1,3-dihydroxythiacalix[4]arene-crowns (3a,c), which could not be obtained by direct bridging of thiacalix[4]arene. The different structures were assigned on the basis of several X-ray crystal structures and extensive 2-D (1)H NMR studies.