Ground and excited state electronic interactions in a bis(phenanthroline) copper(I) complex sandwiched between two fullerene subunits

A new fullerene-substituted phenanthroline ligand has been obtained by reaction of a phenanthroline derivative bearing a 1,3-phenylenebis(methylene)-tethered bis-malonate with C(60) in a double Bingel cyclopropanation. The relative position of the two cyclopropane rings in the resulting bis-methanofullerene derivatives has been determined on the basis of the molecular symmetry (C(s)()) deduced from the (1)H and (13)C NMR spectra. The corresponding Cu(I) complex F-Cu-F has been prepared in good yields by treatment of the ligand with Cu(CH(3)CN)(4)BF(4). In the resulting multicomponent system, both C(60) moieties are in a tangential orientation relative to their bridging phenyl ring, and the central bis(phenanthroline)Cu(I) core is sandwiched between the two carbon spheres. The electrochemical properties of F-Cu-F suggest the existence of ground-state electronic interactions in this multicomponent array based on the mutual effects exerted by the fullerene units to the bis(2,9-diphenyl-1,10-phenanthroline)Cu(I) complex and vice versa. Close vicinity and electronic interactions between the inorganic core and the peripheral fullerene units are also suggested by increased electronic absorption around 430 nm. The distance between the two moieties is estimated to be 4.3 A by molecular modeling studies. The excited-state properties of F-Cu-F have also been investigated. Photoinduced electron transfer from the central chromophore to the external fullerene units occurs but, surprisingly, only following population of the excited states of the central inorganic unit and not of the external carbon spheres. This is mainly attributed to kinetic factors related to the different nature of the two types of excited states involved, namely charge transfer (excitation on the metal-complexed moiety) vs a localized state (excitation on the fullerene units).     

pi-stacking interactions in cis-Bisfullerene

Experimental, molecular modeling, and model compound studies suggest that favorable fullerene[60] pi-stacking interactions in the ground state and in syn-transition states account for the high cis stereoselectivities observed in the reactions between C(60) and 6, 13-disubstituted pentacenes.     

Hexakis-adducts of [60]fullerene as molecular scaffolds of polynuclear spin-crossover molecules

A family of hexakis-substituted [60]fullerene adducts endowed with the well-known tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand for spin-crossover (SCO) systems has been designed and synthesized. It has been experimentally and theoretically demonstrated that these molecular scaffolds are able to form polynuclear SCO complexes in solution. UV-vis and fluorescence spectroscopy studies have allowed monitoring of the formation of up to six Fe(ii)–bpp SCO complexes. In addition, DFT calculations have been performed to model the different complexation environments and simulate their electronic properties. The complexes retain SCO properties in the solid state exhibiting both thermal- and photoinduced spin transitions, as confirmed by temperature-dependent magnetic susceptibility and Raman spectroscopy measurements. The synthesis of these complexes demonstrates that [60]fullerene hexakis-adducts are excellent and versatile platforms to develop polynuclear SCO systems in which a fullerene core is surrounded by a SCO molecular shell.

Polynuclear spin-crossover molecules showing both thermal and photoinduced spin transitions have been prepared using a [60]fullerene hexakis-adduct endowed with Fe(ii) complexes of tridentate 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligand.     

Ruthenium(III) chloride complex with a tridentate bis(arylimino)pyridine ligand: synthesis, spectra, X-ray structure, 9-ethylguanine binding pattern, and in vitro cytotoxicity

The synthetic, spectroscopic, structural, and biological studies of a bis(arylimino)pyridine Ru(III) chloride compound containing the ligand, 2,6-bis(2,4,6-trimethylphenyliminomethyl)pyridine are reported. The bis(arylimino)pyridine ligand, with three donor nitrogen atoms, was synthesized by condensation of 2,6-pyridinedicarboxaldehyde with 2,4,6-trimethylaniline. The Ru(III) complex, with formula [RuCl 3(L1)](H 2O) (RuL1), where L1 = 2,6-bis(2,4,6-trimethylphenyliminomethyl)pyridine, was structurally determined on the basis of analytical and spectroscopic (IR, UV-vis, ESI-MS) studies. A straightforward strategy to fully characterize the paramagnetic compound using advanced (1)H NMR is reported. This new complex is a prototype for a series of new anticancer Ru(III) and Ru(II) compounds with improved cytostatic properties; likely to be modified in a desirable manner due to the relatively facile ligand modification of the bis(imino)pyridines and their molecular architecture. The present Ru(III) complex is the first example of this family of Ru(III)/Ru(II) anticancer compounds with the aimed physicochemical characteristics. Although the ligand itself is moderately active in selected cell lines (EVSA-T and MCF-7), the activity of the [Ru(L1)Cl 3] complex has increased significantly for a broad range of cancer cell lines tested in vitro (IC 50 values = 11 approximately 17 microM). Reaction of the RuL1 species with the DNA model base 9-ethylguanine (9EtGua) was found to produce in a redox reaction the species trans-[Ru(II)(L1)(9EtGua) 2(H 2O)](ClO 4) 2 (abbreviated as RuL1-9EtGua), which was studied in solution and also in the solid state, by X-ray crystallography. The structure comprises the as yet unknown trans-bis(purine)Ru(II) unit.     

A Tunable,Fullerene-Based Molecular Amplifier for Vibrational Circular Dichroism

Vibrational circular dichroism (VCD) studies are reported on a chiral compound in which a fullerene C₆₀ moiety is used as an electron acceptor and local VCD amplifier for an alanine-based peptide chain. Four redox states are investigated in this study, of which three are reduced species that possess low-lying electronic states as confirmed by UV/Vis spectroelectrochemistry. VCD measurements in combination with (TD)DFT calculations are used to investigate (i) how the low-lying electronic states of the reduced species modulate the amplification of VCD signals, (ii) how this amplification depends on the distance between oscillator and amplifier, and (iii) how the spatial extent of the amplifier influences amplification. These results pave the way for further development of tailored molecular VCD amplifiers.     

Heteroleptic copper(I) complexes coupled with methano[60]fullerene: synthesis, electrochemistry, and photophysics

Heteroleptic copper(I) complexes CuPOP-F and CuFc-F have been prepared from a fullerene-substituted phenanthroline ligand and bis[2-(diphenylphosphino)phenyl] ether (POP) and 1,1'-bis(diphenylphosphino)ferrocene (dppFc), respectively. Electrochemical studies indicate that some ground-state electronic interaction between the fullerene subunit and the metal-complexed moiety are present in both CuPOP-F and CuFc-F. Their photophysical properties have been investigated by steady state and time-resolved UV-vis-NIR luminescence spectroscopy and nanosecond laser flash photolysis in a CH2Cl2 solution and compared to those of the corresponding model copper(I) complexes CuPOP and CuFc and of the fullerene model compound F. Selective excitation of the methanofullerene moiety in CuPOP-F results in regular deactivation of the lowest singlet and triplet states, indicating no intercomponent interactions. Conversely, excitation of the copper(I)-complexed unit (405 nm, 40% selectivity) shows that the strongly luminescent triplet metal-to-ligand charge-transfer ((3)MLCT) excited state located at 2.40 eV is quenched by the carbon sphere with a rate constant of 1.6 x 10(8) s(-1). Details on the mechanism of photodynamic processes in CuPOP-F via transient absorption are hampered by the rather unfavorable partition of light excitation between the two chromophores. By determination of the yield of formation of the lowest fullerene triplet level through sensitized singlet oxygen luminescence in the NIR region, it is shown that the final sink of photoinduced processes is always the fullerene triplet. This can be populated via a two-step charge-separation charge-recombination process and a less favored (3)MLCT --> (3)C60 triplet-triplet energy-transfer pathway. In CuFc-F, both of the photoexcited copper(I)-complexed and fullerene moieties are quenched by the presence of the ferrocene unit, most likely via ultrafast energy transfer.     

Synthesis and photophysics of a linear non-covalently linked porphyrin-fullerene dyad

The synthesis and characterization of a new pyridinofullerene ligand capable of forming axially symmetric complexes with ZnTPP is reported; molecular modelling studies, 1H NMR, UV-Vis spectroscopy and fluorescence quenching data support formation of a strong complex between the new ligand and ZnTPP.     

Rapid insight into C60 influence on biological functions of proteins

Experimental methods of investigations of nanoparticle (NP)–protein interactions are limited, because they require a high amount of samples and the NPs tend to interfere with spectral results. Therefore, molecular modeling is a commonly accepted tool in such kind of investigations. Examining the molecule toxicity on the molecular level, we usually want to know, mainly, the location of the ligand on the protein surface and what is an influence of such a contact on the biological functions of the protein. In the presented work, we demonstrate that multiple-docking of the ligand from a random start and with large grid volume, to let the ligand search the whole protein surface, allows to find the best binding sites and gives reliable results considering ligand–protein interactions. In the present work, we have constructed six models of bronchoalveolar lavage fluids proteins: α1-antitripsin, albumin, ceruloplasmin, lactoferrin, lysozyme, and transferrin with fullerene, C₆₀ utilizing molecular docking methods. The most probable results were examined with steered molecular dynamics (SMD) to see, if the simple docking method is able to predict the fullerene binding affinity. Albumin and lysozyme were already widely investigated and literature data is available for their complexes with fullerene C₆₀ and/or its derivatives. Thus, we used these two models as a reference set to validate the used molecular modeling methods. With our best knowledge, interactions of the remaining four proteins with NPs have never been investigated in detail before. Our results indicate that fullerene C₆₀ readily interacts with all studied proteins and may have a large impact on their biological functions.     

Hydroxyfullerene as a novel coating for solid-phase microextraction fiber with sol-gel technology

Hydroxyfullerene (fullerol) as a novel coating for solid-phase microextraction (SPME) fiber was first prepared by a sol-gel technology. The coating procedure involving sol solution composition and conditioning process was presented. A fullerene polysiloxane surface-bonded porous coating on the fused-silica fiber surface was obtained and confirmed by IR spectra and scanning electron microscopy. The coating has stable performance at high temperature (even to 360 degrees C) and solvents (organic and inorganic) because of the properties of fullerene and the chemical binding between the coating and the fiber surface. The extraction properties of the new coatings to less volatile organic compounds, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons and polar aromatic amines were investigated using headspace SPME coupled with GC-electron-capture detection and GC-flame ionization detection. In addition, compared with commercial SPME stationary phases, the new coatings showed higher sensitivity, faster velocities of mass transfer for aromatic compound, and possessed planarity molecular recognition for PCBs. Moreover, this fiber was firm, inexpensive, durable and can be prepared simply. The fiber-to-fiber reproducibility was very good.     

酞菁一富勒烯给受体体系研究进展

酞菁的大π共轭体系使其具有良好的电子给予能力和对可见光的强烈吸收性质,可作为人工光合作用体系中的光捕捉单元．富勒烯具有独特的三维笼状结构,几乎所有反应中都具有低的重组能,是良好的电子或能量受体．将富勒烯与酞菁结合起来,集两个光活性实体于一身,由于酞菁和富勒烯给受体之间的电子相互作用,又赋予其新的性质,具有良好的应用前景,是富勒烯和酞菁领域中的研究热点．本文将酞菁．富勒烯给受体体系分为共价和非共价两种连接方式,介绍其结构与性质以及两者的相互关系,总结了其在有机太阳能电池、非线性光学和液晶性等方面的应用进展,展望了该体系的未来发展趋势．     

C60Pt(CO)(Pph3)配合物的合成及氧化还原性能研究

采用配体取代法,即在惰性气氛下以C60取代Pt(CO)2(Pph3)2中的CO及Pph3,合成了C60Pt(CO)(Pph3)富勒烯金属配合物,利用元素分析、红外光谱、紫外可见光谱、光电子能谱等手段对产物进行鉴定和表征,结果表明,C60以σ-π配位方式与Pt形成了稳定的η2型C60配合物.由于该分子存在超共轭作用,分子内电子流动性大,因而该配合物可能具有良好的光电转化性能及催化性能.氧化还原性能研究表明,C60在与金属有机基团Pt(CO)(Pph3)形成配合物后,其还原电位向负方向发生了移动.     

Anisotropic pseudorotation of the photoexcited triplet state of fullerene C60 in molecular glasses studied by pulse EPR

Spin-polarized echo-detected electron paramagnetic resonance (EPR) spectra and the transversal relaxation rate T2(-1) of the photoexcited triplet state of fullerene C60 molecules were studied in o-terphenyl, 1-methylnaphthalene, and decalin glassy matrices. The model is composed of a fast (correlation time approximately 10(-12) s) pseudorotation of (3)C60 in a local anisotropic potential created by interaction of the fullerene molecule with the surrounding matrix molecules. In simulations, this potential is assumed to be axially symmetric around some axis of a preferable orientation in a matrix cage. The fitted value of the potential was found to depend on the type of glass and to decrease monotonically with a temperature increase. A sharp increase of the T2(-1) temperature dependence was found near 240 K in glassy o-terphenyl and near 100 K in glassy 1-methylnaphthalene and decalin. This increase probably is related to the influence on the pseudorotation of the onset of large-amplitude vibrational molecular motions (dynamical transition in glass) that are known for glasses from neutron scattering and molecular dynamics studies. The obtained results suggest that molecular and spin dynamics of the triplet fullerene are extremely sensitive to molecular motions in glassy materials.     

Photoswitchable Norbornadiene–Quadricyclane Interconversion Mediated by Covalently Linked C60

The synthesis and properties of various norbornadiene/quadricyclane (NBD/QC) fullerene hybrids are reported. By cyclopropanation of C₆₀ with malonates carrying the NBD scaffold a small library of NBD–fullerene monoadducts and NBD–fullerene hexakisadducts was established. The substitution pattern of the NBD scaffold, as well as the electron affinity of the fullerene core within these hybrid systems, has a pronounced impact on the properties of the corresponding energy rich QC derivatives. Based on this, the first direct photoisomerization of NBD–fullerene hybrids to their QC derivatives was achieved. Furthermore, it was possible to use the redox-active fullerene core of a QC–fullerene monoadduct to enable the back reaction to form the corresponding NBD–fullerene monoadduct. Combining these two processes enables switching between NBD and QC simply by changing the irradiation wavelength between 310 and 400 nm. Therefore, turning this usually photo/thermal switch into a pure photoswitch. This not only simplifies the investigation of the underlying processes of the NBD–QC interconversion within the system, but also renders such hybrids interesting for applications as molecular switches.     

[60]Fullerene diol issued from pentaerythritol derivatives

A new [60]fullerene diol is synthesized in good yield, in two steps starting from reaction of C₆₀²⁻ anion with the benzylideneacetal derived from 2,2-bis(iodomethyl)-1,3-propanediol. The corresponding [60]fullerene bis-mesylate is also formed in a similar way starting from bis-iodo bis-mesylate compound in the same series. The scope of this fullerene diol in synthesis is exemplified by its easy esterification with 4-formyl benzoyl chloride.     

Pentasubstituted ferrocene and dirhodium(II) tetracarboxylate as building blocks for discrete fullerene-like and extended supramolecular structures

The synthesis of a penta(1-methylpyrazole)ferrocenyl phosphine oxide ligand (1) [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))] is reported together with its X-ray crystal structure. Its self-assembly behavior with a dirhodium(II) tetraoctanoate linker (2) [Rh(2)(O(2)CC(7)H(15))(4)] was investigated for construction of fullerene-like assemblies of composition [(ligand)(12)(linker)(30)]. Reaction between 1 and 2 in acetonitrile resulted in the formation of a light purple precipitate (3). Evidence for the ligand-to-linker ratio of 1:2.5 expected for a fullerene-like structure [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))](12)[Rh(2)(O(2)CC(7)H(15))(4)](30) was obtained from (1)H NMR and elemental analysis. IR and Raman studies confirmed the diaxially bound coordination environment of the dirhodium linker by comparing the stretching frequencies of the carboxylate group and the rhodium-rhodium bond with those in model compound (5), [Rh(2)(O(2)CC(7)H(15))(4)](C(3)H(3)N(2)CH(3))(2), the bis-adduct of linker 2 with 1-methylpyrazole. X-ray powder diffraction and molecular modeling studies provide additional support for the formation of a spherical molecule topologically identical to fullerene with a diameter of approximately 38 ? and a molecular formula of [(1)(12)(2)(30)]. Dissolution of 3 in tetrahydrofuran (THF) followed by layering with acetonitrile afforded purple crystals of [(1)(2)(2)](∞) (6) [Fe(C(5)(C(3)H(2)N(2)CH(3))(5))(C(5)H(4)PO(t-C(4)H(9))(2))][Rh(2)(O(2)CC(7)H(15))(4)](2) with a two-dimensional polymeric structure determined by X-ray crystallography. The dirhodium linkers link ferrocenyl units by coordination to the pyrazoles but only four of the five pyrazole moieties of the pentapyrazole ligand are coordinated. The ligand-to-linker ratio of 1:2 in 6 was confirmed by (1)H NMR spectroscopy and elemental analysis, while results from IR and Raman are in agreement with the diaxially coordinated environment of the linker observed in the solid state.     

Hierarchical Corannulene‐Based Materials: Energy Transfer and Solid‐State Photophysics

We report the first example of a donor–acceptor corannulene‐containing hybrid material with rapid ligand‐to‐ligand energy transfer (ET). Additionally, we provide the first time‐resolved photoluminescence (PL) data for any corannulene‐based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand‐to‐ligand ET rate calculated using two models is comparable with that observed in fullerene‐containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π‐bowls, specifically corannulene derivatives, with the versatility of crystalline hybrid scaffolds, but could also foreshadow the engineering of a novel class of hierarchical corannulene‐based hybrid materials for optoelectronic devices.     

Synthesis of a new C60-substituted tris(2,2′-bipyridine)ruthenium(II) complex

A new tris(2,2′-bipyridine)ruthenium(II) complex substituted with two fullerene subunits has been prepared starting from a fullerene carboxylic acid derivative and a 2,2′-bipyridine ligand bearing two alcohol functions.     

A molecular dynamics simulation study of C60 fullerenes inside a dimyristoylphosphatidylcholine lipid bilayer

We have carried out atomistic molecular dynamics simulations of C60 fullerenes inside a dimyristoylphosphatidylcholine lipid bilayer and an alkane melt. Simulations reveal that the preferred position of a single C60 fullerene is about 6-7 A off of the center plane, allowing the fullerene to take advantage of strong dispersion interactions with denser regions of the bilayer. Further displacement (>8 A) of the fullerene away from the center plane results in a rapid increase in free energy likely due to distortion of the lipid head group layer. The effective interaction between fullerenes (direct interaction plus environment (bilayer)-induced interaction), measured as the potential of mean force (POMF) between two fullerenes as a function of their separation, was found to be significantly less attractive in the lipid bilayer than in an alkane melt of the same molecular weight as the lipid tails. Only part of this difference can be accounted for by the more favorable interaction of the fullerene with the relatively denser bilayer. Additionally, our POMF studies indicate that the bilayer is less able to accommodate the larger aggregated fullerene pair than isolated single fullerenes, again likely due to distortion of the bilayer structure. The implications of these effects on aggregation of fullerenes within lipid bilayer are considered.     

2-(2,5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯的合成和电子光谱的理论研究

利用丙氨酸和2,5-二羟基苯甲醛所形成的亚胺叶立德与C₆₀发生1,3-偶极环加成反应, 合成并分离、纯化制备了一种新的C₆₀吡咯烷衍生物: 2-(2-5-二羟基苯基)-5-甲基-2,5-二氢吡咯并[3,4]富勒烯. 通过¹H NMR, FT-IR, UV-vis和元素分析确定了其结构, 研究了体系的电化学和荧光性质. 采用密度泛函的方法, 在B3LYP/6-31G水平上对分子的几何构型进行了优化, 得到稳定的几何构型; 运用INDO/S方法计算了化合物的电子光谱, 计算结果434.2 nm与实验值432.0 nm基本一致.     

Critical Role of Molecular Electrostatic Potential on Charge Generation in Organic Solar Cells

Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non‐fullerene organic solar cells (OSCs) indicates efficient charge separation even with negligible energetic offset between the donor and acceptor materials. These new findings trigger a critical question concerning the charge separation mechanism in OSCs, traditionally believed to result from sufficient energetic offset between the polymer donor and fullerene acceptor. We propose a new mechanism, which involves the molecular electrostatic potential, to explain efficient charge separation in non‐fullerene OSCs. Together with the new mechanism, we demonstrate a record efficiency of ~12% for systems with negligible energetic offset between donor and acceptor materials. Our analysis also rationalizes different requirement of the energetic offset between fullerene‐based and non‐fullerene OSCs, and paves the way for further design of OSC materials with both high photocurrent and high photovoltage at the same time.