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The need to harvest low-grade waste heat at 100–200 °C has attracted much attention.

Orbital angular momentum plays a vital role in various applications, especially magnetic and spintronic properties. Therefore, controlling orbital angular momentum is of paramount importance to both fundamental science and new technological applications. Many attempts have been made to modulate the ligand-field induced quenching effects of orbital angular momentum to manipulate magnetic properties. However, to date, reported changes in the magnitude of orbital angular momentum are small in both molecular and solid-state magnetic materials. Moreover, no effective methods currently exist to modulate orbital angular momentum. Here, we report a dynamic bond approach to realize a large change in orbital angular momentum. We have developed a Co(II) complex that exhibits coordination number switching between six and seven. This cooperative dynamic bond switching induces considerable modulation of the ligand field, thereby leading to substantial quenching and restoration of the orbital angular momentum. This switching mechanism is entirely different from those of spin-crossover and valence tautomeric compounds, which exhibit switching in spin multiplicity.

A Prussian Blue (PB) film formed on an indium tin oxide substrate was incorporated in an electrolysis cell with an ionic-liquid midlayer (N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide) as an electrolyte. The ionic-liquid electrolysis cell mounted on a SQUID magnetometer was examined under DC bias voltage up to 4.0 V by injecting the charge carriers electrochemically into the PB film. Electrochemical hole doping increased the FeIII/FeII ratio in the PB film, resulting in a remarkable enhancement of magnetization accompanied by quasi-reversible electrochromism.

A nickel film with electrical conductivity was successfully synthesized via thermal decomposition. A complex consisting of nickel formate ink and triethylenetetramine was coated onto a glass substrate, which was then calcined under a nitrogen atmosphere. The ink complex then became electrically conductive nickel film and showed a bright surface. As the molar ratio of amine to nickel formate was increased, the volume resistivity of the nickel film was decreased to an almost constant level at ratios higher than 2. The volume resistivity of the nickel film was decreased with an increase in the temperature, which resulted in a lower resistivity of 460 μΩ cm at 230 °C, and then it was slightly increased at higher temperatures. The obtained nickel film consisted of particles that were approximately 100–200 nm in diameter, which were connected to one another by a bridge-like structure with many voids.

The ability to switch a molecule between different magnetic states is of considerable importance for the development of new molecular electronic devices. Desirable properties for such applications include a large-spin ground state with an electronic structure that can be controlled via external stimuli. Fe

Herein is described a new method for the fabrication of copper conductive films at temperatures of less than 100 °C. This method uses self-reducible copper complex inks and two types of amines. Copper complex inks with only 3-butylpyridine are capable of self-reducing at temperatures below 100 °C, but the process is accompanied by the formation of cracks that results in metallic copper films that are highly resistive. The combination of 3-butylpyridine and dipropylamine in self-reducible copper complex inks prevents the generation of cracks via the connection of self-reduced copper particles in the film, which results in low volume resistivity.

A one-step direct fabrication of thin-film manganese oxide electrodes was accomplished via low-temperature thermal decomposition of inks composed of manganese formate (Mnf), alkylamines, and hexanol. As complexing agents, amines were used in molar ratios of Mnf:amine that ranged from 1:1 to 1:4. Prepared inks were directly coated onto the substrate, and then calcined at 170–210 °C under air. Cyclic voltammetry and charge/discharge measurements of the thin films were conducted in an electrolyte solution. Following immersion, the specific capacitance of the electrodes increased and eventually reached a constant value. Based on the results of cyclic voltammetry (CV) at 1 mV s−1, a thin-film electrode fabricated at 180 °C from Mnf-octylamine-hexanol ink at a molar ratio of 1:3:0.5 had the highest level of specific capacitance at 400 F g−1. CV measurement at 1000 cycles revealed a deterioration of specific capacitance of only 5%, which indicates good stability for this thin-film electrode.

Flexible porous materials generally switch their structures in response to guest removal or incorporation. However, the design of porous materials with empty shape-switchable pores remains a formidable challenge. Here, we demonstrate that the structural transition between an empty orthorhombic phase and an empty tetragonal phase in a flexible porous dodecatuple intercatenated supramolecular organic framework can be controlled cooperatively through guest incorporation and thermal treatment, thus inducing empty shape-memory nanopores. Moreover, the empty orthorhombic phase was observed to exhibit superior thermoelasticity, and the molecular-scale structural mobility could be transmitted to a macroscopic crystal shape change. The driving force of the shape-memory behaviour was elucidated in terms of potential energy. These two interconvertible empty phases with different pore shapes, that is, the orthorhombic phase with rectangular pores and the tetragonal phase with square pores, completely reject or weakly adsorb N2 at 77 K, respectively., Designing porous materials with empty shape-switchable pores remains a formidable challenge. Here, the authors fabricate a supramolecular organic framework possessing empty shape-memory nanopores which operates via a ferroelastic transition, endowing it with switchable sorption properties.

Heterometallic Prussian blue analogues are known to exhibit thermally induced charge transfer, resulting in switching of optical and magnetic properties. However, charge-transfer phase transitions have not been reported for the simplest FeFe cyanide-bridged systems. A mixed-valence Fe(II) /Fe(III) cyanide-bridged coordination polymer, {[Fe(Tp)(CN)3 ]2 Fe(bpe)⋅5 H2 O}n , which demonstrates a thermally induced charge-transfer phase transition, is described. As a result of the charge transfer during this phase transition, the high-spin state of the whole system does not change to a low-spin state. This result is in contrast to FeCo cyanide-bridged systems that exhibit charge-transfer-induced spin transitions.

The anionic Fe(III) complex exhibiting cooperative spin transition with a wide thermal hysteresis near room temperature, K[Fe(5-Brthsa)2 ] (5-Brthsa-H2 =5-bromosalicylaldehyde thiosemicarbazone), is reported. The hysteresis (Δ=69 K in the first cycle) shows a one-step transition in heating mode and a two-step transition in cooling mode. X-ray structure analysis showed that the coexistence of hydrogen bond and cation-π interactions, as well as alkali metal coordination bonds, to give 2D coordination polymer structure. This result is contrary to previous reports of broad thermal hysteresis induced by coordination bonds of Fe(II) spin crossover coordination polymers (with 1D/3D structures), and by strong intermolecular interactions in the molecular packing through π-π stacking or hydrogen-bond networks. As a consequence, the importance, or the very good suitability of alkali metal-based coordination bonds and cation-π interactions for communicating cooperative interactions in spin-crossover (SCO) compounds must be reconsidered.

The crystal of a valence tautomeric cobalt complex, [Co(dbbq)2(bpym)](1) (dbbq = 3,6-di-tert-butyl-1,2-benzoquinone and bpym = 2,2′-bipyrimidine), have been obtained by reaction between Co2(CO)8 and dbbq in the presence of the ligand bpym in a mixed solvent under an N2 atmosphere. The magnetic behavior of complex 1 clearly indicates that electron transfer from the catecholate ligand to the CoIII center occurs, which results in valence tautomers of [CoII(SQ)2(bpym)] with a transition temperature (T1/2) of 232(1) K. Photomagnetic studies show that complex 1 exhibits photoinduced valence tautomerism. The complex has the ability to coordinate and can be used as a photoswitchable building block.

The preparation and characterization of two new FeII dinuclear complexes with bis-tetradentate bridging-type ligands [{Fe(NCS)2}2(L)]·DMF·2H2O (1: L = L1{2,5-bis[N,N-bis(2-pyridylmethyl)aminomethyl]pyrazine}, 2: L = L2{2,3-bis[N,N-bis(2-pyridylmethyl)aminomethyl]pyrazine}) are reported. Magnetic measurements reveal that complexes 1 and 2 exhibit different thermal spin-crossover behavior. Complex 1 shows a crystalline solvent effect on spin crossover (SCO). After desorption of the crystalline solvent by heating, an abrupt one-step transition with a hysteresis loop was observed for the desolvated form 1′. Conversely, a gradual two-step SCO was obtained for 2. The photomagnetic effect was also investigated in 1′ and 2, and both complexes clearly show light-induced excited spin state trapping. Interestingly, one-step and two-step thermal relaxation were observed for 1′ and 2, respectively. Such different SCO properties occur because of the cooperative effects owing to the structure of the ligand.

The polarization switching mechanism is used in various devices such as pyroelectric sensors and memory devices. The change in polarization mostly occurs by ion displacement. The development of materials whose polarization switches via electron transfer in order to enhance operation speed is a challenge. We devised a synthetic and crystal engineering strategy that enables the selective synthesis of a [CrCo] heterometallic dinuclear complex with a polar crystal structure, wherein polarization changes stem from intramolecular charge transfer between Co and the ligand. Polarization can be modulated both by visible-light irradiation and temperature change. The introduction of chiral ligands was paramount to the successful polarization switching in the valence tautomeric compound. Mixing Cr and Co complexes with enantiopure chiral ligands resulted in the selective formation of only pseudosymmetric [CrCo] heterometallic complexes. Furthermore, the left-handed chiral ligands preferentially interacted with their right-handed counterparts, enabling molecules to form a polar crystal structure.

Proton transport via dynamic molecules is ubiquitous in chemistry and biology. However, its use as a switching mechanism for properties in functional molecular assemblies is far less common. In this study, we demonstrate how an intra-carboxyl proton shuttle can be generated in a molecular assembly akin to a rack-and-pinion cascade via a thermally induced single-crystal-to-single-crystal phase transition. In a triply interpenetrated supramolecular organic framework (SOF), a 4,4′-azopyridine (azpy) molecule connects to two biphenyl-3,3′,5,5′-tetracarboxylic acid (H4BPTC) molecules to form a functional molecular system with switchable mechanical properties. A temperature change reversibly triggers a molecular movement akin to a rack-and-pinion cascade, which mainly involves 1) an intra-carboxyl proton shuttle coupled with tilting of the azo molecules and azo pedal motion and 2) H4BPTC translation. Moreover, both the molecular motions are collective, and being propagated across the entire framework, leading to a macroscopic crystal expansion and contraction.

Two polymorphic structures have been well determined in a valence tautomeric (VT) dinuclear cobalt complex. These polymorphs showdistinct thermal and photo magnetic behaviors, and are thus, ideal for studyingthe "pure" intermolecular factors to VT transitions. In polymorph 1A, the VT cations are arranged head-to-waist with their neighbors and exhibit weak pai-pai interactions, resulting in a gradual and incomplete thermal VT transition. In contrast, the cations in polymorph 1B are arranged head-to-tail and exhibit relatively strong pai-pai interactions, leading to an abrupt and complete thermal VT transition with adjustable hysteresis loop at around room temperature. The VT process for both polymorphs can be induced by light, but the light-excited state of 1B*2H2O has a higher thermal relaxation temperature than that of 1A*3H2O.

Atypically anisotropic and large changes in magnetic susceptibility, along with a change in crystalline shape, were observed in a CoII complex at near room temperature. This was achieved by combining oxalate molecules, acting as rotor, and a CoII ion with unquenched orbital angular momentum. A thermally controlled 90° rotation of the oxalate counter anion triggered a symmetry-breaking ferroelastic phase transition, accompanied by contraction-expansion behavior (ca. 4.5 %) along the long axis of a rod-like single crystal. The molecular rotation induced a minute variation in the coordination geometry around the CoII ion, resulting in an abrupt decrease and a remarkable increase in magnetic susceptibility along the direction perpendicular and parallel to the long axis of the crystal, respectively. Theoretical calculations suggested that such an unusual anisotropic change in magnetic susceptibility was due to a substantial reorientation of magnetic anisotropy induced by slight disruption in the ideal D3 coordination environment of the complex cation.

Trifluoroacetic acid-catalyzed condensation of pyrrole with electron-deficient and sterically hindered 3,5-bis(trifluoromethyl)benzaldehyde results in the unexpected production of a series of meso-3,5-bis(trifluoromethyl)phenyl-substituted expanded porphyrins including [22]sapphyrin 2, N-fused [22]pentaphyrin 3, [26]hexaphyrin 4, and intact [32]heptaphyrin 5 together with the conventional 5,10,15,20-tetrakis(3,5-bis(trifluoromethyl)phenyl)porphyrin 1. These expanded porphyrins are characterized by mass spectrometry, (1)H NMR spectroscopy, UV/Vis/NIR absorption spectroscopy, and fluorescence spectroscopy. The optical and electrochemical measurements reveal a decrease in the HOMO-LUMO gap with increasing size of the conjugated macrocycles, and in accordance with the trend, the deactivation of the excited singlet state to the ground state is enhanced.

Multiporphyrin-modified CdSe nanoparticles (CdSe-H2P) were prepared to elucidate the interaction between chromophores and luminescent semiconducting nanoparticles in the excited and ground states. The CdSe-H2P nanoparticles were obtained by place-exchange reactions of hexadecylamine-thiophenol-modified CdSe nanoparticles with porphyrin alkanethiols in toluene. The number of porphyrin molecules on the surface of a single CdSe nanoparticle increased with increasing reaction time to reach a saturated maximum of 21. The porphyrins as well as the core in CdSe-H2P can absorb UV/Vis radiation. Steady-state emission and emission-lifetime measurements reveal efficient energy transfer from the CdSe excited state to the porphyrins in the CdSe-H2P nanoparticles. The resulting porphyrin excited singlet state is not quenched by the CdSe core. These unique properties are in sharp contrast with those of multiporphyrin-modified metal and silica nanoparticles. Thus, semiconducting nanoparticle-multiporphyrin composites are highly promising as novel artificial photosynthetic materials.

We have systematically examined the substituent effects of meso-tetraphenylporphyrins on film structures and the photoelectrochemical properties of the composite clusters of free-base porphyrin and C(60) electrophoretically deposited on nanostructured SnO(2) electrodes. The photocurrent generation efficiency was found to correlate with the complexation ability of the porphyrin for C(60). Basically, the incident photon-to-current efficiency (IPCE) value was increased with increasing relative amounts of the porphyrin versus C(60) in the films. The unique molecular arrangement of the porphyrin with the simple, specific substituents (i.e., methoxy groups at the meta-positions of the meso-phenyl rings of tetraphenylporphyrins (3,5-OMeTPP; TPP=tetraphenylporphyrin)) and C(60) on SnO(2) electrodes resulted in the largest IPCE value (ca. 60 %) among this type of photoelectrochemical device. The rapid formation of the composite clusters and microcrystals from the combination of 3,5-OMeTPP and C(60) in a mixed solvent is unique as the association is accelerated by intermolecular interactions (i.e., hydrogen-bonding and CH-pi interactions) between the methoxy groups of the porphyrins and the porphyrin/C(60), in addition to the pi-pi interactions between the porphyrins/C(60) and C(60) molecules. Both the films and single crystals composed of the porphyrin and C(60) exhibited remarkably high electron mobility (7x10(-2) and 0.4 cm(2) V(-1) s(-1)), which is comparable to the value for highly efficient bulk heterojunction solar cells. Our experimental results have successfully demonstrated the importance of nanostructured electron- and hole-transporting pathways in bulk heterojunction solar cells. Such a finding will provide basic and valuable information on the design of molecular photovoltaics at the molecular level.

Harnessing molecular motion to reversibly control macroscopic properties, such as shape and size, is a fascinating and challenging subject in materials science. Here we design a crystalline cobalt(II) complex with an n-butyl group on its ligands, which exhibits a reversible crystal deformation at a structural phase transition temperature. In the low-temperature phase, the molecular motion of the n-butyl group freezes. On heating, the n-butyl group rotates ca. 100° around the C–C bond resulting in 6–7% expansion of the crystal size along the molecular packing direction. Importantly, crystal deformation is repeatedly observed without breaking the single-crystal state even though the shape change is considerable. Detailed structural analysis allows us to elucidate the underlying mechanism of this deformation. This work may mark a step towards converting the alkyl rotation to the macroscopic deformation in crystalline solids., Molecular motion can potentially be harnessed to control macroscopic properties such as size and shape. Here, the authors show that the phase transition of a cobalt(II) complex with an n-butyl group on its ligands, results in a reversible crystal deformation at the structural phase transition temperature.

Self-assembly of artificial nanoscale units into superstructures is a prevalent topic in science. In biomimicry, scientists attempt to develop artificial self-assembled nanoarchitectures. However, despite extensive efforts, the preparation of nanoarchitectures with superior physical properties remains a challenge. For example, one of the major topics in the field of molecular magnetism is the development of high-spin (HS) molecules. Here, we report a cyanide-bridged magnetic nanocage composed of 18 HS iron(III) ions and 24 low-spin iron(II) ions. The magnetic iron(III) centres are ferromagnetically coupled, yielding the highest ground-state spin number (S=45) of any molecule reported to date., One area of interest in the field of molecular magnetism is the development of high-spin molecules. Here, the authors report a cyanide-bridged nanocage consisting of 18 high-spin iron(III) ions ferromagnetically coupled through 24 low-spin iron(II) ions, with a ground state spin of S=45.

Structure and photoelectrochemical properties of nanostructured SnO2 electrodes deposited electrophoretically with the composite clusters of porphyrin-modified gold nanoparticle with a long, flexible spacer and C60 molecules have been examined to obtain basic information on the development of organic solar cells with a high performance. The photoelectrochemical system with the long, flexible spacer between the porphyrin and the gold nanoparticle in the porphyrin-modified gold nanoparticle exhibited comparable external quantum yield in the UV–vis regions relative to porphyrin-modified gold nanoparticle with a relatively short spacer—C60 composite reference system. These results demonstrate that a suitable spacer to incorporate C60 molecules efficiently between the porphyrins in porphyrin-modified gold nanoparticles is a prerequisite for improving the performance of porphyrin and fullerene-based organic solar cells.

Electroabsorption and electrofluorescence spectra of a fullerene derivative, C60(C18)2, and its mixture with zinc-tetraphenylporphyrin (ZnTPP) have been measured by using electric field modulation spectroscopy. The change in dipole moment is significant in the electroabsorption spectra both of C60(C18)2 and of a complex composed of C60(C18)2 and ZnTPP, indicating that the excited states both of C60(C18)2 and of a complex between C60(C18)2 and ZnTPP have a large charge-transfer character. The fluorescence quantum yield of C60(C18)2 decreases in the presence of an electric field, which probably arises from the field-induced acceleration of the intramolecular nonradiative process of C60(C18)2 in the fluorescent state. In a mixture between ZnTPP and C60(C18)2, electrofluorescence spectra show the field-induced enhancement for the fluorescence of ZnTPP and the field-induced de-enhancement for the fluorescence both of C60(C18)2 and of the complex between ZnTPP and C60(C18)2. A theoretical analysis clearly shows that the field-induced enhancement of the ZnTPP fluorescence in a mixture results from the field-induced deceleration of the rate of the electron transfer from the excited ZnTPP to C60(C18)2. The standard free energy gap for the photoinduced electron-transfer process is estimated based on the theoretical simulation of the field-dependent fluorescence intensity.

Many molecular machines with controllable molecular-scale motors have been developed. However, transmitting molecular movement to the macroscopic scale remains a formidable challenge. Here we report a single crystal of a Ni complex whose shape changes abruptly and reversibly in response to thermal changes at around room temperature. Variable-temperature single-crystal X-ray diffraction studies show that the crystalline shape change is induced by an unusual 90° rotation of uniaxially aligned oxalate molecules. The oxalate dianions behave as molecular-scale rotors, with their movement propagated through the entire crystalline material via intermolecular hydrogen bonding. Consequently, the subnanometre-scale changes in the oxalate molecules are instantly amplified to a micrometre-scale contraction or expansion of the crystal, accompanied by a thermal hysteresis loop. The shape change in the crystal was clearly detected under an optical microscope. The large directional deformation and prompt response suggest a role for this material in microscale or nanoscale thermal actuators.

An oligothiophene bearing 1-hydroxy-1-oxodithieno[2,3-b:3′,2′-d]phosphole (TP) as a novel anchoring group has been synthesized for dye-sensitized solar cells (DSSC). Attenuated total reflectance-Fo...

Spin-crossover complexes and single-chain magnets exhibit magnetic bistability and may be used in information storage applications. Here, the authors present a one-dimensional spin-crossover complex wherein the single-chain magnet behaviour is actuated by light-induced excited spin-state trapping.

The reaction of Co(NO(3))(2)·6H(2)O and 3-benzoylpyridine with the low-spin iron(III) complex, H[Fe(III)(phen)(CN)(4)], in methanol gives rise to a cyanide-bridged heterobimetallic chain [{Fe(III)(phen)(CN)(4)}(2)Co(II)(3-bpe)(2)] (1) that exhibits intrachain ferromagnetic coupling and slow double magnetic relaxation.

Time resolved absorption spectroscopy has been used to study photoinduced electron injection and charge recombination in Zn-porphyrin sensitized nanostructured TiO(2) electrodes. The electron transfer dynamics is correlated to the performance of dye sensitized solar cells based on the same electrodes. We find that the dye/semiconductor binding can be described with a heterogeneous geometry where the Zn-porphyrin molecules are attached to the TiO(2) surface with a distribution of tilt angles. The binding angle determines the porphyrin-semiconductor electron transfer distance and charge transfer occurs through space, rather than through the bridge connecting the porphyrin to the surface. For short sensitization times (1 h), there is a direct correlation between solar cell efficiency and amplitude of the kinetic component due to long-lived conduction band electrons, once variations in light harvesting (surface coverage) have been taken into account. Long sensitization time (12 h) results in decreased solar cell efficiency because of decreased efficiency of electron injection.

Electrode structures and photovoltaic properties of porphyrin-sensitized solar cells with TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were examined to disclose the effects of partial substitution of Ti atom by the other metals in the composite electrodes. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were prepared by sol-gel process using laurylamine hydrochloride as a template for the formation of micellar precursors yielding well-defined mesoporous nanocrystalline structures, as in the cases of the formation of silica and titania tubules and nanoparticles by the templating mechanism. The TiO2 and Nb-, Ge-, and Zr-added TiO2 composite electrodes were characterized by transmission electron microscopy, BET surface area analysis, X-ray diffraction analysis, Raman spectroscopy, and impedance measurements. The TiO2 anatase nanocrystalline structure is retained after doping a small amount (5 mol %) of Nb, Ge, or Zr into the TiO2 structure, suggesting the homogeneous distribution of the doped metals with replacing Ti atom by the doped metal. The power conversion efficiency of the porphyrin-sensitized solar cells increases in the order Zr-added TiO2 (0.8%)Nb-added TiO2 (1.2%)TiO2 (2.0%)Ge-added TiO2 cells (2.4%) under the same conditions. The improvement of cell performance of the Ge-added TiO2 cell results from the negative shift of the conduction band of the Ge-added TiO2 electrode. The Ge-added TiO2 cell exhibited a maximum power conversion efficiency of 3.5% when the porphyrin was adsorbed onto the surface of the Ge-added TiO2 electrode with a thickness of 4 microm in MeOH for 1 h.

Two kinds of fullerene derivatives have been designed to examine the effect of the fullerene substituents on the structure and photoelectrochemical properties of fullerene clusters electrophoretically deposited on nanostructured SnO(2) electrodes. The cluster sizes increase and the incident photon-to-current efficiencies decrease with introduction of large substituents into C(60). The trend for photocurrent generation efficiency as well as surface morphology on the electrode can be explained by the steric bulkiness around the C(60) molecules. A C(60) molecule with two alkoxy chains is suggested to give a bilayer vesicle structure, irrespective of the hydrophobic nature of both the C(60) and alkoxy chain moieties. Such information will be valuable for the design of photoactive molecules, which are fabricated onto electrode surfaces to exhibit high energy conversion efficiency.

Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. The porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C 6 0 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C 6 0 composites (second step). Large composite clusters with a size of 200-400 nm were grown from the supramolecular complex of porphyrin-C 6 0 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO 2 electrodes (fourth step). Differences in the porphyrin:& ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO 2 electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO 2 electrodes modified with the porphyrin-C 6 0 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle. Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C 6 0 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C 6 0 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photovoltaics.

Solid-state nuclear magnetic resonance (NMR) has been applied to “amorphous” active layers consisting of donor-acceptor self-assembled composites in organic solar cells. Several stoichiometric supramolecular complexation states as well as the charge-transfer states are revealed by the solid-state NMR, which have been difficult to access by conventional spectroscopy. The spectra show clear correlation between local self-assembled supramolecular structures and the organic solar cell performances.

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