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Developing molecular circuits that can function as the active components in electrical devices is an ongoing challenge in molecular electronics. It demands mechanical stability of the single-molecule circuit while simultaneously being responsive to external stimuli mimicking the operation of conventional electronic components. Here, we report single-molecule circuits based on spiropyran derivatives that respond electrically to chemical and mechanical stimuli. The merocyanine that results from the protonation/ ring-opening of the spiropyran form showed single-molecule diode characteristics, with an average current rectification ratio of 5 at ±1 V, favoring the orientation where the positively charged end of the molecule is attached to the negative terminal of the circuit. Mechanical pulling of a single spiropyran molecule drives a switch to a more conducting merocyanine state. The mechanical switching is enabled by the strong Au−C covalent bonding between the molecule and the electrodes, which allows the tensile force delivered by the STM piezo to break the molecule at its spiropyran C−O bond.

High resolution synchrotron and neutron single crystal diffraction data of 18-crown-6:(pentakis)urea measured at 30 K are combined, with the aim to better appreciate the electrostatics associated with intermolecular interactions in condensed matter. With two 18-crown-6 molecules and five different urea molecules in the crystal, this represents the most ambitious combined X-ray/synchrotron and neutron experimental charge density analysis to date on a co-crystal or host-guest system incorporating such a large number of unique molecules. Dipole moments of the five urea guest molecules in the crystal are enhanced considerably compared with values determined for isolated molecules, and 2D maps of the electrostatic potential and electric field show clearly how the urea molecules are oriented with dipole moments aligned along the electric field exerted by their molecular neighbors. Experimental electric fields in the range 10-19 GV m-1 , obtained for the five different urea environments, corroborate independent measurements of electric fields in the active sites of enzymes, and provide an important experimental reference point for recent discussions focused on electric-field-assisted catalysis.

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The reaction of N,N'-bis(trimethylsilyl)ethylenediamine with H(3)Al.NMe(3) gives products based on metalation (H(2) elimination), [{[CH(2)N(SiMe(3))](2)AlH}(2)] (1) and [{CH(2)N(SiMe(3))}(2)AlN(SiMe(3))CH(2)CH(2)N(H)SiMe(3)] (2), as well as products derived from N-Si bond cleavage and metalation, [{[CH(2)N(SiMe(3))](2)AlH}(2){HAlN(SiMe(3))CH(2)CH(2)NAlH(2)}] (4) and [H(2)Al{CH(2)N(SiMe(3))}(2)AlN(SiMe(3))CH(2)CH(2)NAl(H)(2).NMe(3)}] (5). Similarly, [Me(3)SiN(H)CH(2)CH(2)N(SiMe(3))AlCl(2)] (3) was isolated as the redistributed/metalated product from the reaction of the same diamine with H(2)Al(Cl).NMe(3). The following crystal data were obtained: (1) monoclinic, space group P2(1)/c (No. 14), a = 13.636(4) Å, b = 9.565(3) Å, c = 22.683(4) Å, beta = 105.67(2) degrees, Z = 4; (2) monoclinic, space group C2/c (No. 15), a = 31.887(3) Å, b = 10.145(6) Å, c = 17.718(3) Å, beta = 100.36(1) degrees, Z = 8; (3) triclinic, space group P&onemacr; (No. 2), a = 11.762(3) Å, b = 11.927(3) Å, c = 7.288(2) Å, alpha = 107.46(2) degrees, beta = 95.29(2) degrees, gamma = 110.41(2) degrees, Z = 2; (4) triclinic, space group P&onemacr; (No. 2), a = 13.884(4) Å, b = 15.379(4) Å, c = 11.044(2) Å, alpha = 102.11(2) degrees, beta = 103.85(2) degrees, gamma = 109.28(2) degrees, Z = 2; (5) triclinic, space group P&onemacr; (No. 2), a = 10.925(5) Å, b = 11.060(5) Å, c = 12.726(4) Å, alpha = 92.38(3) degrees, beta = 95.67(2) degrees, gamma = 96.90(2) degrees, Z = 2.