Hexylene‐ and Octylene‐Bridged Polysilsesquioxane Hybrid Crystals Self‐Assembled by Dimeric Building Blocks with Ring Structures

Abstract

We report the synthesis of novel polysilsesquioxane hybrid crystals prepared from two precursors with hexylene- and octylene-bridged groups. Both crystals are composed of bimolecular rings (18- and 22-membered, respectively) formed by one-step condensation of two hydrolyzed monomers. The hydrogen bonds between silanol groups and the weak van der Waal's interactions between alkyl chains link the large rings as building blocks together into self-assembled, three-dimensional molecular crystalline structures. The precise control of the sol-gel process is considered to be the crucial factor in fabricating flexible long alkyl chains into an ordered stacking. These contributions extend the understanding of the sol-gel chemistry of polysilsesquioxanes.

In situ X‐ray Measurements to Probe a New Solid‐State Polycondensation Mechanism for the Design of Supramolecular Organo‐Bridged Silsesquioxanes

“…Structural ordering was also studied as a function of the chemical nature and geometry of the organic unit (rigid,21 twisted,22 planar,23 or tetrahedral24 organic units). Highly crystalline solids were recently obtained using hybrid precursors with flexible hexylene or octylene chains as organic bridging units and where only weak van der Waals interactions exist between alkyl chains 25. Formerly we showed that reinforcing the intermolecular interactions between the organic fragments with urea groups26 and/or with long alkylene chains27 offered a nice route to self‐directing the structuring of bridged silsesquioxanes.…”

Lanthanide(III)‐Based Multicolor Luminescent Hybrid Gel for Amine Sensing

“…Bands centered at ñ = 956 and 1168 cm À1 in the spectrum of the precursor (Figure 1a)a re ascribed to the absorption of SiOCH 2 CH 3 groups, whichd isappear when the gels are formed, and an ew broad band at ñ = 1130-1000 cm À1 ,w hich is assigned to Si-O-Si, [5d] is observed ( Figure 1b). [7] By comparing the spectrum of Eu 3 + -containing gel (Eu 3 + @BP) to that of the undoped one (TMC-BP), we can observe that the vibration of C=Oe xperiences ad ownshift from ñ = 1656 to 1630 cm À1 upon the introduction of EuCl 3 (Figure 1c), which implies the coordinationo fE u 3 + ions to the C=Og roups. In addition, ac haracteristic band at ñ = 904 cm À1 ,w hichi sa ttributed to noncondensed SiÀOH groups, is also seen;t his provides evidencet hat the condensation is not complete.…”

“…In addition, ac haracteristic band at ñ = 904 cm À1 ,w hichi sa ttributed to noncondensed SiÀOH groups, is also seen;t his provides evidencet hat the condensation is not complete. [7] By comparing the spectrum of Eu 3 + -containing gel (Eu 3 + @BP) to that of the undoped one (TMC-BP), we can observe that the vibration of C=Oe xperiences ad ownshift from ñ = 1656 to 1630 cm À1 upon the introduction of EuCl 3 (Figure 1c), which implies the coordinationo fE u 3 + ions to the C=Og roups. [8] The coordination behavior between TMC-Si and Tb 3 + can be also confirmed from the FTIR spectrum, which displays as imilarv arying pattern (see Figure S3 in the Supporting Information).…”

Conformational and structural stability of the single molecule and hydrogen bonded clusters of para aminobenzoic acid in the gas and solution phases

“…One hypothesis is that the crystallisation of a particular crystalline form may be directed by the relative stability of small cluster building blocks in solution such as dimers or tetramers, which then self-assemble to realise the structural motifs contained within the crystal structure, has been explored extensively in the field of coordination metal-ligand chemistry 25 . Such studies often focus on the self-assembly of complex structures [26][27][28] and, in particular, on tailor-made building blocks that have been designed to induce selfassembly 29,30 . However, some more recent theoretical studies of organic materials have identified solute clusters in solution that resemble the crystalline form produced from different solvents 31-34 . In terms of understanding the nucleation transition pathway in a range of solvents, it is prudent to identify computationally efficient methods of modelling the stability of molecular clusters as a function of the solvation environment.…”