Emergent electronic properties in Co-deposited superatomic clusters

We report an intercluster compound based on co-deposition of the Au cluster [Au₉(PPh₃)₈](NO₃)₃ and the fulleride KC₆₀(THF). Electronic properties characteristic for a charge interaction between superatoms emerge within the solid state material [Au₉(PPh₃)₈](NO₃)_3-x(C₆₀)_x, as confirmed by UV-VIS and Raman spectroscopy and I-V measurements. These emergent properties are related to the superatomic electronic states of the initial clusters. The material is characterized by Fourier-transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, and electrical measurements. Structural optimization and ab initio band structure calculations are performed with density functional theory to interpret the nature of the electronic states in the material; Bader charge calculations assign effective oxidation states in support of the superatomic model of cluster interactions.

Exohedral Functionalization of Fullerene by Substituents Controlling of Molecular Organization for Spontaneous C60 Dimerization in Liquid Crystal Solutions and in a Bulk Controlled by a Potential

A study was carried out on the possibility of orderly and spontaneous dimerization at room temperature of C₆₀ cages in fullerene liquid crystal fullerene dyads (R-C₆₀). For this purpose, dyads with a structural elements feature supporting π-stacking and Van der Waals interactions were tested, due to the presence of terthiophene donors linked through an α-position or dodecyloxy chains. In addition, this possibility was also tested and compared to dyads with shorter substituents and the pristine C₆₀. Research has shown that only in dyads with the features of liquid crystals, π-dimerization of C₆₀ units occurs, which was verified by electrochemical and spectroelectrochemical (ESR) measurements. Cyclic voltammetry and differential voltammetry studies reveal π-dimerization in liquid crystal dyad solution even without the possibility of previous polymerization (cathodic or anodic) under conditions in the absence of irradiation and without the availability of reaction initiators, and even with the use of preliminary homogenization. These dyads undergo six sequential, one-electron reductions of π-dimer (R-C₆₀···C₆₀-R), where two electrons are added successively to each of the two fullerene cages and first form two radical anion system (R-C₆₀)^•−(R-C₆₀)^•− without pairing with the characteristics of two doublets. Similarly, the second reductions of π-dimer occur at potentials that are close to the reduction potential for the conversion to a system of two triplet dianions (R-C₆₀)²⁻(R-C₆₀)²⁻. Electron paramagnetic resonance spectra indicate a significant interaction between C₆₀ cages. Interestingly, the strength of intermolecular bonds is so significant that it can overcome Coulombic repulsion, even with such highly charged particles as dianions and trianions. Such behavior has been revealed and studied so far only in covalently bonded C₆₀ dimers.

The Stoichiometry of TCNQ-Based Organic Charge-Transfer Cocrystals

Organic charge-transfer cocrystals (CTCs) have attracted significant research attention due to their wide range of potential applications in organic optoelectronic devices, organic magnetic devices, organic energy devices, pharmaceutical industry, etc. The physical properties of organic charge transfer cocrystals can be tuned not only by changing the donor and acceptor molecules, but also by varying the stoichiometry between the donor and the acceptor. However, the importance of the stoichiometry on tuning the properties of CTCs has still been underestimated. In this review, single-crystal growth methods of organic CTCs with different stoichiometries are first introduced, and their physical properties, including the degree of charge transfer, electrical conductivity, and field-effect mobility, are then discussed. Finally, a perspective of this research direction is provided to give the readers a general understanding of the concept.

Electronic Communication between S=1/2 Spins in Negatively-charged Double-caged Fullerene C60 Derivative Bonded by Two Single Bonds and Pyrrolizidine Bridge

Radical anion salt {cryptand[2.2.2] (K⁺ )}₂ (bispheroid)^2- ⋅3.5C₆ H₄ Cl₂ (1) of the double-caged fullerene C₆₀ derivative, in which fullerene cages are linked by a cyclobutane bridging cycle and additionally by a pyrrolizidine moiety, was obtained. Each fullerene cage in this derivative accepts one electron on reduction, thus forming the (bispheroid)^2- dianions with two interacting S=1/2 spins on the neighboring cages. Low-temperature magnetic measurements reveal a singlet ground state of the bispheroid dianions whereas triplet contributions prevail at increased temperature. An estimated exchange interaction between two spins J/k_B =-78 K in 1 indicates strong magnetic coupling between them, nearly two times higher than that (J/k_B =-44.7 K) in previously studied (C₆₀ ^- )₂ dimers linked via a cyclobutane bridge only. The enhancement of magnetic coupling in 1 can be explained by a shorter distance between the fullerene cages and, possibly, an additional channel for the magnetic exchange provided by a pyrrolizidine bridge. Quantum-chemical calculations of the lowest electronic state of the dianions by means of multi-configuration quasi-degenerate perturbation theory support the experimental findings.

Endohedral metal-nitride cluster ordering in metallofullerene-NiII(OEP) complexes and crystals: a theoretical study

The ordering of endohedral clusterfullerenes Sc3N@C80 and YSc2N@C80 co-crystallized with Ni(OEP) and isolated complexes with Ni(OEP) have been investigated theoretically. Having used multiple orientations of M3N clusters inside the cages with Fibonacci sampling, we describe the effect of intermolecular interactions on the orientation of the endohedral cluster.

Negatively charged singly-bonded dimers of C1-[C70(CF3)10] and bare C70 fullerene

Singly-bonded {C₇₀(CF₃)₁₀⁻}₂ and (C₇₀⁻)₂ dimers are obtained as crystalline salts allowing their molecular structure, and optical and magnetic properties to be studied.

Light-induced dilation in nanosheets of charge-transfer complexes

We report the observation of a sizable photostrictive effect of 5.7% with fast, submillisecond response times, arising from a light-induced lattice dilation of a molecular nanosheet, composed of the molecular charge-transfer compound dibenzotetrathiafulvalene (DBTTF) and C60 An interfacial self-assembly approach is introduced for the thickness-controlled growth of the thin films. From photoabsorption measurements, molecular simulations, and electronic structure calculations, we suggest that photostriction within these films arises from a transformation in the molecular structure of constituent molecules upon photoinduced charge transfer, as well as the accommodation of free charge carriers within the material. Additionally, we find that the photostrictive properties of the nanosheets are thickness-dependent, a phenomenon that we suggest arises from surface-induced conformational disorder in the molecular components of the film. Moreover, because of the molecular structure in the films, which results largely from interactions between the constituent π-systems and the sulfur atoms of DBTTF, the optoelectronic properties are found to be anisotropic. This work enables the fabrication of 2D molecular charge-transfer nanosheets with tunable thicknesses and properties, suitable for a wide range of applications in flexible electronic technologies.

Polarizability as a landmark property for fullerene chemistry and materials science

The review summarizes data on dipole polarizability of fullerenes and their derivatives, covering the most widespread classes of fullerene-containing molecules (fullerenes, fullerene exohedral derivatives, fullerene dimers, endofullerenes, fullerene ions, and derivatives with ionic bonds).

Design, crystal structures and magnetic properties of anionic salts containing fullerene C60 and indium(iii) bromide phthalocyanine radical anions

Salts containing fullerene C₆₀ and indium(iii) bromide phthalocyanine (Pc) radical anions, (TBA⁺)₃(C₆₀˙⁻){In^III(Br)(Pc)˙⁻}(Br⁻)·C₆H₄Cl₂ (1) and (TEA⁺)₂(C₆₀˙⁻){In^III(Br)(Pc)˙⁻}·C₆H₄Cl₂·C₆H₁₄ (2), have been obtained and their structures, optical and magnetic properties are discussed.

Synthesis, electron transport, and charge storage properties of fullerene–zinc porphyrin hybrid nanodiscs

A MIS-type diode (Ag/C₆₀–ZnTANP circular discs/p-Si/Ag) has been fabricated and its charge storage properties have been explored.

Transition from free rotation of C70 molecules to static disorder in the molecular C70 complex with covalently linked porphyrin dimers: {(FeIIITPP)2O}·C70

Fullerene C 70 and covalently linked porphyrin ( Fe III TPP )2 O dimers (TPP: tetraphenylporphyrin) form molecular complex {( Fe III TPP )2 O }· C 70 (1). Each C 70 molecule is sandwiched between two ( Fe III TPP )2 O dimers and is surrounded by phenyl groups of four other porphyrin dimers. At 295 K, C 70 molecules freely rotate about the short axis of the molecule in the ab plane. As a result, the disordered C 70 molecules form spheroids flattened at the poles. The rotation of C 70 stops near 100 K, resulting in the transition from a tetragonal to a monoclinic unit cell with a four-fold increase in the unit cell volume. In monoclinic phase the C 70 molecules are located on the axis which coincides with the short axis of the molecule and passes through the midpoints of two oppositely located 6-6 bonds. Since this position has higher symmetry than the own symmetry of C 70, it results in statistic disorder of the C 70 molecules between two orientations. It was shown that multiple Van der Waals contacts with a concave Fe III TPP macrocycle which appear below 100 K, play an important role in the ordering of C 70.

Fullerene complexes with cobalt(II) tetraphenylporphyrin: from molecular to ionic crystals

The complexes of cobalt(II) tetraphenylporphyrin ( Co II TPP ) with fullerenes C 60, C 70 and C 60( CN )2 are presented. It is shown that Co II TPP forms complexes with fullerenes in different solvents: [ Co II TPP •fullerene•solvent] ( solvent = C 6 H 6, C 6 H 5 Me , C 6 H 4 Cl 2, CS 2, CHCl 3). The use of additional donors ( Cp 2 Fe , Cr 0( C 6 H 6)2, and TDAE ) in the synthesis of Co II TPP /fullerene complexes allows one to obtain multi-component complexes ranging from neutral [( Co II TPP • Py )2• Cp 2 Fe • fullerene • solvent ] to ionic [ Co II TPP •( D 2•+)•( fullerene •−)• solvent ] ( D 2 = Cr I( C 6 H 6)2, TDAE ). The interaction of Co II TPP with neutral and negatively charged fullerenes is considered. The neutral Co II TPP /fullerene complexes are characterized by a secondary M…C(fullerene) bonding with the shortest Co … C contacts in the 2.69-2.82 Å range and noticeable changes in the electronic structure of the parent components. At the same time, σ-bonding is observed in ionic complexes between Co II TPP and fullerene radical anions with the shortened Co … C contacts being in the 2.28-2.32 Å range. The resulting ( Co II TPP •fullerene−) anions are diamagnetic. The σ-bonding is relatively weak and the ( Co II TPP •fullerene−) anions begin to dissociate above 200 K.

Molecular and ionic complexes of pyrrolidinofullerene bearing chelating 3-pyridyl units

Molecular and ionic complexes of cis-2',5'-di(pyridin-3-yl)pyrrolidino[3',4':1,9](C(60)-I(h))[5,6]fullerene DP3FP with chlorobenzene (C(6)H(5)Cl), manganese(II) tetraphenylporphyrin (Mn(II)TPP) and tetrakis(dimethylamino)ethylene (TDAE) have been obtained for the first time. X-ray single crystal structure determination for the crystalline DP3FP·C(6)H(5)Cl (1) solvate proved unambiguously its molecular structure with the cis-arrangement of chelating 3-pyridyl groups. It has been demonstrated that DP3FP easily forms self-assembled photoactive complexes with metallated porphyrins. For example, the formation of a 1 : 1 complex between DP3FP and zinc (II) tetraphenylporphyrin (Zn(II)TPP) in cyclohexane solution (2) was evidenced using absorption spectroscopy. A successful X-ray single crystal structure determination was performed for a self-assembled triad composed of a DP3FP molecule linked with two Mn(II)TPP molecules in {DP3FP·(Mn(II)TPP)(2)}·(C(6)H(4)Cl(2))(3) (3). A strong organic donor TDAE reduces DP3FP to the radical anion state thus forming an ionic complex (TDAE˙(+))·(DP3FP˙(-))·(C(6)H(4)Cl(2))(1.6) (4). Optical, electronic and magnetic properties of 4 were investigated in detail. The performed studies strongly suggest that pyrrolidinofullerene DP3FP can be used as a building block in the design of various organic materials with advanced optoelectronic and/or magnetic properties.