The search for voluminous stators that may accommodate large rotator units and speed rotational dynamics in the solid state led us to investigate a simple and efficient method for the synthesis of molecular rotors with tert-butyldiphenylsilyl-protected (TBDPS) triphenylmethyl stators. Additionally, solid state characterization of these systems with two-, four-, and six-TBDPS groups provided us with a description of their crystallinity and thermal stability. Among them, molecular rotor 7c with the largest and most symmetric stator resulting from six peripheral silyl groups showed the best tendency to crystallize, and the study of its isotopologue 7c-d(4) by solid state (2)H NMR revealed a 2-fold motion of the 1,4-diethynylphenylene-d(4) rotator in the kHz regime.

In this work, we describe the synthesis and solid-state characterization of a series of molecular rotors with tri-isopropylsilyloxy-substituted (TIPS) trityl stators axially linked to 1,4-diethynylphenylene, 3,6-diethynyl-1,2-difluorophenylene and 2,5-diethynylpyridine rotators to produce 1,4-bis [(3,3- (3). The subsequent removal of the TIPS protecting group led to their corresponding hydroxyl-substituted trityl derivatives (4) and (5). TIPS-and HO-substituted stators are involved in different inter-and intramolecular interactions (hydrogen bonding, phenyl embraces, C-H-p interactions) that give rise to isomorphic packing motifs that constrained the rotational dynamics in the solid-state to the slow exchange regime. Crystallographic Data Centre as supplementary publication nos. CCDC 943819 (4a-acetone), 943820 (4b-methanol), 943821 (4c-DMSO), 943496 (2) and 943497 (1), these data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.uk/data_request/cif. See Fig. 7 Crystal packing of solvates 4 in (a) acetone 4a, (b) DMSO 4c and (c) methanol 4b, view along b axis. Scheme 2 Synthesis of molecular rotors 4 and 5.This journal is

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The synthesis and solid-state characterization of a series of cyclic/acyclic molecular rotors derived from naturally occurring steroidal 12-oxosapogenins are described. The bridged molecular rotors with rigid steroidal frameworks were obtained by employing ring-closing metathesis (RCM) as a key step. The X-ray diffraction technique was employed for determination and refinement of the crystal and molecular structure of selected models giving good quality single crystals. In the case of the bridged hecogenin molecular rotor 11E for which poor quality crystals were obtained, an NMR crystallography approach was used for fine refinement of the structure. Solid state NMR spectroscopic techniques were applied for the study of local molecular dynamics of the featured acyclic/cyclic molecular rotors. Analysis of 13 C principal components of chemical shift tensors and chemical shift anisotropy (CSA) as well as heteronuclear 1 H− 13 C dipolar couplings (DC) unambiguously proved that aromatic rings located in the space within the rigid steroidal framework both for cyclic and acyclic rotors are under kHz exchange regime. Experimental results were confirmed by theoretical calculations of rotation barrier on the density functional theory level. Small distinctions in the values of CSA and DC for the rotors under investigation are explained on the basis of differences in their molecular structures.

The promising class of (polypyridine-ruthenium)-nitrosyl complexes capable of high yield Ru-NO/Ru-ON isomerization is targeted as a potential molecular device for the achievement of complete NLO switches in the solid state. A computational investigation conducted at the PBE0/6-31+G** DFT level for benchmark systems of general formula [R-terpyridine-Ru II Cl 2 (NO)](PF 6 ) (R being a substituent with various donating or withdrawing capabilities) leads to the suggestion that an isomerization could produce a convincing NLO switch (large value of the b ON /b OFF ratio) for R substituents of weak donating capabilities. Four new molecules were obtained in order to test the synthetic feasibility of this class of materials with R = 4 0 -p-bromophenyl, 4 0 -p-methoxyphenyl, 4 0 -p-diethylaminophenyl, and 4 0 -p-nitrophenyl. The different cis-(Cl,Cl) and trans-(Cl,Cl) isomers can be separated by HPLC, and identified by NMR and X-ray crystallographic studies.