Zinc porphyrins equipped with pyridine ligands form macrocyclic assemblies in organic solvents. The assemblies have been characterised by 1H NMR, UV-visible spectroscopy, X-ray crystallography and vapour pressure osmometry. The self-assembly properties of six isomeric porphyrins are relatively insensitive to the geometry of the porphyrin monomer. Changes in the internal torsion angles allow all of the porphyrins to form macrocyclic dimers but with differences in the relative orientations of the porphyrin units. The associated strain reduces the effective molarities from the value of 6 M reported previously for an ‘ideal’ monomer to between 0.07 and 2 M leading to dimerisation constants in the 105–106 M−1 range. Only one isomer has a geometry that makes dimerisation impossible without severe distortion, and this compound self-assembles to give a tetrameric macrocycle at millimolar concentrations.

An air-stable organic conducting polymer, polypyrrole (PPy), has been deposited from aqueous solution onto micrometer-sized Thermally Expandable Microspheres (TEMs). These polypyrrole-coated TEM particles were characterized using scanning electron microscopy, laser diffraction, FT-IR and Raman spectroscopy and also uv-visible reflectance spectroscopy. Polypyrrole has a broad absorption peak in the near infra-red at around 900–1500 nm, hence irradiation of the polypyrrole-coated TEM particles using an infra-red lamp (λmax = 1200 nm) leads to efficient localized heating that causes the TEM particles to expand to many times their original volume. Hot-stage optical microscopy studies confirm that this large volumetric change is not constrained by the conducting polymer overlayer: expansion of the polypyrrole-coated TEM particles is at least as effective as that found for uncoated TEM particles subjected to conventional bulk heating. Moreover, thermal expansion achieved via infra-red irradiation is significantly quicker and leads to cleaner delamination. Thus this approach seems to be well suited to niche applications such as the reversible adhesion of car glazing and panels, which are likely to play an important role in the future for both convenient repair of increasingly complex composite materials and also end-of-lifetime manufacturer-led recycling initiatives.

Mixtures of isomers are available from the reaction of benzene hexathiol with three equivalents of p-tolualdehyde and kinetic traps avoided under the reported catalytic conditions, establishing tris(thioacetals) as potential building blocks for covalently self-assembled complex structures.

Two cobalt(II) porphyrin-C(60) malonate-linked conjugates, the mono-connected Co1 and the bis-connected trans-2 isomer Co3, have been synthesized for the first time either by direct cyclopropanation with the precursor malonate Co4 or by metalation of the bisadduct H(2)3. For the investigation of the interaction between the porphyrin donor and fullerene acceptor within these dyads, electrochemical and photophysical investigations have been carried out. Compared to Zn3 and trans-2 bisadduct 7, the first reduction of the fullerene moiety within Co3 becomes easier (40 mV in dichloromethane and 20 mV in benzonitrile), indicating significant interactions between the pi-system of the fullerene and the d-orbitals of the central Co atom. Compared to the Co complexes 9, Co4, and Co1, the first oxidation of Co3 is considerably shifted to more positive potentials, if benzonitrile instead of dichloromethane is used as solvent. At the same time, the oxidation is no longer centered on the Co(II) center but on the porphyrin macrocycle, as corroborated by spectroelectrochemistry. A similar solvent dependence was observed in transient absorption spectroscopic measurements. In toluene, benzonitrile and anisole photoinduced electron transfer within Co3 leads to the formation of a charge-separated state Co(II)P.+ -C(60).- with a lifetime of 560 +/- 20 ns in benzonitrile, whereas in other solvents such as THF, nitrobenzene, ortho-diclorobenzene, and tert-butylbenzene the formation of a Co(III)P-C(60).- as transient was detected, which is, however, short-lived (860 +/- 40 ps in THF) and exhibits charge recombination dynamics that are in the Marcus inverted region. Particularly important is the fact that the electronic coupling (V) in Co(III)P-C(60).- is 18 cm(-1) substantially smaller than the V value of 313 cm(-1) in ZnP.+ -C(60).- .

Density functional theory energies, geometries, and population analyses as well as nucleus-independent chemical shifts (NICS) have been used to investigate the structural and magnetic evidence for cyclic CnSn(2-) and CnSn (n = 3-6) electron delocalization. Localized molecular orbital contributions to NICS, computed by the individual gauge for localized orbitals method, dissect pi effects from the sigma single bonds and lone pair influences. CnSn(2-) (n = 3-5) structures in Dnh symmetry are minima. Their aromaticity decreases with increasing ring size. C3S3(2-) is both sigma and pi aromatic, while C4S4(2-) and C5S5(2-) are much less aromatic. NICS(0)pi, the C-C(pi) contribution to NICS(0) (i.e., at the ring center), decreases gradually with ring size. In contrast, cyclic C6S6(2-) prefers D2h symmetry due to the balance between aromaticity, strain energy, and the S-S bond energies and is as aromatic as benzene. The theoretical prediction that C6S6(6-) has D6h minima was confirmed by X-ray structure analysis. Comparisons between thiocarbons and oxocarbons based on dissected NICS analysis show that CnSn(2-) (n = 3-5) and C6S6(6-) are less aromatic in Dnh symmetry than their oxocarbon analogues.