Self-assembly in the solid state

Polyferrocenylsilane block copolymers in which the blocks are immiscible (which is generally the case) would be expected to self-assemble to form phase-separated organometallic domains in the solid state. Based on the classical behavior of organic block copolymers, thin films of polyferrocene diblock copolymers would be expected to form domains such as spheres, cylinders, double diamonds (or gyro-ids) (or their antistructures), or lamellae (Chapter 1, Section 1.2.5). The preferred domain structure would be expected to be controlled by the ratio of the blocks, their degree of immiscibility (as defined by the Flory-Hu ins interaction parameter x), and the overall molecular weight of the block copolymer [159]. 

The first studies of polyferrocenylsilane block copolymer films were reported in 1996 and utilized DSC and TEM to analyze the phase separation in the materials (83j. In the case of PS-b-PFS (3.54) and PFS-b-PDMS (3.52), it was demonstrated that the electron-rich Fe atoms of the polyferrocenylsilane block cause sufficient electron scattering to provide contrast with the organic or inorganic coblocks, so that selective staining of one of the blocks, which is generally required for all-or- 

Pyrolysis of phase-separated PFS block copolymer films also allows the formation of metal-rich nanostructures. For example, pyrolysis of a thin film of PS-b-PFS, with cylinders of the amorphous PFS block oriented perpendicular to the substrate within a crosslinked PS matrix, at 600 °C yields iron-containing dots of size ca. 20 nm on a substrate (Fig. 3.19) [168]. 

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The chiral l,3,5-triazepane-2,6-dione 149 and its ring fused analogue 150 have been shown to form H-bonded helical molecular tapes with P chirality on self assembly in the solid state. With 149, this self assembly proceeds through aromatic-aromatic ring interactions resulting in hollow tubular structures <06CC4069>. 

Shenhar R, Sanyal A, Uzun O, Nakade H, Rotello VM. Integration of recognition elements with macromolecular scaffolds effects on polymer self-assembly in the solid state. 

Examples of supramolecular association as a result of intermolecular organolead-sulphur interactions are rare and compounds such as Me3PbSMe and Pl PbSPh are monomeric in the solid state463. In contrast, triphenyllead pyridine-4-thiolate, d-Pl PbSCsFLjN464, is a chain polymer as a result of intermolecular N—Pb interactions. The cyclic dithiolate 2,2-diphenyl-l,3,2-dithiaplumbolane 177465 self-assembles in the solid state via intermolecular tin-sulphur interactions into a one-dimensional polymeric array. The intramolecular Pb—S bond lengths amount to 2.52(2) and 2.49(1) A and the intermolecular Pb—S distances are 3.55(2) A. 

Examples of association resnlting from intermolecular sulfur organolead hypervalent interactions are rare and componnds snch as MeyPbSMe and Ph3PbSPh are monomeric in the solid state. The cyclic diorgano dithiolate 2,2-diphenyl-l,3,2-dithiaplnmbolan ° self-assembles in the solid state via intermolecular sulfur tin interactions into a onedimensional polymeric array. The intramolecular S Pb bond lengths amonnt to 2.52 and 2.49 A, and the intermolecnlar S Pb distances are 3.55 A. 

Triorganotin derivatives of l-phenyl-177-tetrazole-5-thiol also tend to self-assemble in the solid state . For example, tribenzyltin 1-phenyl-177-tetrazole-5-thiolate, Bz3SnSCN4Ph (161), forms a linear coordination polymer with intermolecular Sn—N distances of 2.559(12) and 2.676(10) A and intramolecular Sn—S distances of 2.565(4) A , whereas trimethyltin 1-phenyl-177-tetrazole-5-thiolate, Me3SnSCN4Ph °, self-assembles to give trimers. 

Molecular Self-Assembly in the Solid State Molecular Organic Crystals... 

Unsymmetrical U-shaped molecules with two different hydrogen-bonding groups that give homodimers have also been reported. Specifically, a molecular cleft known as Rebek s imide has been shown to self-assemble in the solid state via two N-H -O and two O-H -O hydrogen bonds of two imide-carboxylic acid synthons (Fig. 4).11... 

An example of a molecule that self-assembles to give a finite 3D assembly is triphenylmethanol.32 The alcohol has been shown to self-assemble in the solid state, via O-H-O hydrogen bonds, to form a tetramer, with the point group C3 and a structure that conforms to a molecular tetrahedron (Fig. 14). The hydrogen bonds exhibited substantial dynamic disorder in the solid. Each molecule sits at the corner of the tetrahedron with the phenyl rings in propeller-like conformations. 

Rebek has conducted extensive studies on curve-shaped molecules that self-assemble to form homodimers, in the form of molecular capsules, in both solution and the solid state.34 In particular, Valdes et al. have demonstrated the ability of two glycoluril units separated by a benzene spacer to self-assemble in the solid state via eight N-H O hydrogen bonds to form a capsule with a structure that conforms to a tennis ball (Fig. 16).34a A disordered guest, identified as probably being methanol, occupied the interior. A related dimer based on an ethylene spacer was also prepared and shown to accommodate a guest, also identified as probably being methanol, in the crystalline state.34b... 

Bohmer has reported the ability of a bowl-shaped molecule known as a calixarene to self-assemble in the solid state to form a homodimer.35 A calix[4]arene with four urea groups attached to the upper rim self-assembled via 16 hydrogen bonds to give a cavity with an approximate volume of 200 A3 (Fig. 17). The cavity hosted a highly... 

Mascal has demonstrated the ability of a bent molecule with AAD and DDA sequences of hydrogen bonds to self-assemble in the solid state to form a cyclic... 

A tetrameric capsule of ideal D2 symmetry has been reported by Rebek.65 In particular, a molecule with glycoluril and sulfamide functionality self-assembled in the solid state via 24 hydrogen bonds to form a finite assembly that accommodated 2,6-adamantanedione as a guest. The volume of the cavity of the capsule was determined to be approximately 184 A3 (Fig. 35). Each carbonyl oxygen atom of the... 

Crystal deconstruction is the process that leads backwards. in a reverse "aufbau process, from the structure of a molecular crystal to the component molecules or ions. Crystal deconstruction allows one to focus on the interactions that are more relevant for crystal structure cohesion. The objective of the deconstruction process is also that of learning about the factors responsible for molecular/ionic recognition and self-assembly in the solid state. Insights into crystal polymorphism can be gained by comparing the different distributions of intermolecular interactions associated with the existence of different crystal forms of the same molecular species. 

Guarrera, D. Taylor, L.D. Warner, J.C. Molecular Self-Assembly in the Solid State. The Combined Use of Solid-State NMR and Differential Scanning Calorimetry for the Determination of Phase Constitution. Chem. Mater. 1994, 5, 1293. 

The triorganotin(IV) 1-phenyl-17/-tetrazole-5-thiolates, R3SnSCN4R, (R = Me, Bu, Ph, R = Me, Ph) were found to be monomeric in solution, but spectroscopic data suggest that all are self-assembled in the solid state [293]. 

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