Large Torsion Angle Research Articles

Biological Response of the Intervertebral Disc to Repetitive Short-Term Cyclic Torsion

In vitro study of the biological response of the intervertebral disc (IVD) to cyclic torsion by using bovine caudal IVDs. To evaluate the biological response of the IVD to repetitive cyclic torsion of varying magnitudes at a physiological frequency. Mechanical loading is known to be a risk factor for disc degeneration (DD) but the role of torsion in DD is controversial. It has been suggested that a small magnitude of spinal rotation decreases spinal pressure, increases spinal length, and enhances nutrition exchange in the IVD. However, athletes who participate actively in sports involving torsional movement of the spine are frequently diagnosed with DD and/or disc prolapse. Bovine caudal discs with end plates were harvested and kept in custom-made chambers for in vitro culture and mechanical stimulation. Torsion was applied to the explants for 1 hour/day over four consecutive days by using a servohydraulic testing machine. The biological response was evaluated by cell viability, metabolic activity, gene expression, glycosaminoglycan content, and histological evaluation. A significantly higher cell viability was found in the inner annulus of the 2˚ torsion group than in the static control group. A trend of decreasing metabolic activity in the nucleus pulposus with increasing torsion magnitude was observed. Apoptotic activity in the nucleus pulposus significantly increased with 5˚ torsion. No statistical significant difference in gene expression was found between the three torsion angles. No visible change in matrix organization could be observed by histological evaluation. The IVD can tolerate short-term repetitive cyclic torsion, as tested in this study. A small angle of cyclic torsion can be beneficial to the IVD in organ culture, possibly by improving nutrition and waste exchange, whereas large torsion angle may cause damage to disc in the long term.

Coumarin dyes containing low-band-gap chromophores for dye-sensitised solar cells

A series of coumarin dyes containing a low-band-gap chromophore of ethylenedioxythiophene (EDOT), which comprises a coumarin moiety as the electron donor and a cyanoacrylic acid moiety as electron acceptor in D–π–A chromophores, were developed for use in dye-sensitised solar cells (DSSCs). These coumarin dyes have been used to fabricate DSSCs using I −/I 3 − liquid electrolytes and their device performances were compared with that of NKX-2677 as a standard dye. Even though HKK-CM2 and HKK-CM3 have more extended aromatic units than HKK-CM1, the degree of π-conjugation in HKK-CM2 and HKK-CM3 is less efficient than that of HKK-CM1, due to the relatively larger torsion angle between the plane of the donor and that of the acceptor. It is also in a good agreement with Density Functional Theory (DFT) calculations. As a result, a solar cell based on HKK-CM1 sensitiser shows better photovoltaic performance with J SC of 14.2 mA cm −2, V OC of 0.60 V, and a fill factor of 0.70, corresponding to an overall conversion efficiency η of 6.07% under the standard AM 1.5 irradiation, than HKK-CM2 and HKK-CM3-based solar cells.

多台阶平板静电驱动的高占空比微镜阵列的研制

In order to obtain a micro-mirror array with large torsional angles and large sizes under limited driving voltages,a novel micro-mirror array with a multi-terraced-plate structure was proposed and demonstrated based on the Micro-optoelectro mechanical System(MOEMS).The different characteristics of the electrostatic driver between multi-terraced-plate structure and parallel-plate structure were analyzed.The key fabrication process for the multi-terraced-plate structure was researched and a bulk micro-mechanical technology was used to fabricate a micro-mirror array with the multiterraced-plate structure.The obtained micro-mirror array contaning 52 micromirrors has the size in 600 μm by 200 μm,and a high fill-factor in excess of 97%.The test results show that the micro-mirror array achieves a maximum torsional angle about 1.1° under a driving voltage of 164 V,and the multi-terraced-plate structure greatly reduces the driving voltage as compared with the traditional parallel-plate structure.

Energetics and electronic structure of phenyl-disubstituted polyacetylene: A first-principles study

Phenyl-disubstituted polyacetylene (PDPA) is an organic semiconductor which has been studied during recent years for its efficient photoluminescence. In contrast, the molecular geometry, providing the basis for the electronic and optical properties has been hardly investigated. In this paper, we apply a density-functional-theory based molecular-dynamics approach to reveal the molecular structure of PDPA in detail. We find that oligomers of this material are limited in length, being stable only up to eight repeat units, while the polymer is energetically unfavorable. These facts, which are in excellent agreement with experimental findings, are explained through a detailed analysis of the bond lengths. A consequence of the latter is the appearance of pronounced torsion angles of the phenyl rings with respect to the plane of the polyene backbone, ranging from $55\ifmmode^\circ\else\textdegree\fi{}$ up to $95\ifmmode^\circ\else\textdegree\fi{}$. We point out that such large torsion angles do not destroy the conjugation of the $\ensuremath{\pi}$ electrons from the backbone to the side phenyl rings, as is evident from the electronic charge density.

Micromachining SU-8 pivot structures using AZ photoresist as direct sacrificial layers for a large wing displacement

This paper presents the micromachining of SU-8 pivot structures. A new processing method was proposed using AZ 4562 as sacrificial layers to create a controlled air gap in the pivot region. These three-dimensional SU-8 pivot structures are designed to obtain a large wing displacement of the bio-mimetic flying micromachine. Several sacrificial methods used for the fabrication of SU-8 structures were reviewed and compared. A new process featuring AZ 4562 sacrificial layers was developed. Two relevant effects, the scission and outgassing effects, were greatly weakened to acquire a better SU-8/AZ interface. It was found that AZ 4562 could be directly deposited on SU-8 without any barrier layer between AZ 4562 and SU-8. So, AZ 4562 can be used directly as a thick sacrificial layer, thus greatly simplifying the fabrication process. SU-8 reinforcing patches can be added to compensate for the loss in the thickness of the central beam in the pivot regions. Using this new method, SU-8 pivot structures with different central beams, either straight or L-shaped, were successfully materialized. The air gap obtained was large and reached ∼100 µm, thus helping to produce a large wing displacement. The fabrication precision and its main factors were evaluated. The deviation of actual structure size from design value was 2–7%, depending on the material and technique involved. Preliminary measurements of the fabricated structure indicating that a large wing displacement, flexure angle and torsion angle can be achieved. This new process is simple, low cost and compatible with standard MEMS technology.

(5S,6S)-4,5-Dimethyl-3-methylacryloyl-6-phenyl-1,3,4-oxadiazinan-2-one

The title compound, C15H18N2O3, is an example of an oxadiazinan-2-one with significant inter­action between the N3-acyl and N4-methyl groups. These steric inter­actions result in a large torsion angle between the two carbonyl groups, not present with acyl substituents with less steric demand.

Synthesis, Structure, and Properties of Benzoquinone Dimer and Trimers Bearing t-Bu Substituents

Highly soluble and stable quinone dimer and trimers were successfully yielded by introduction of t-Bu substituents. In X-ray structure analysis, the dimer quinone moiety was distorted into the boat shape, which was clarified by MO calculations. X-ray and UV/vis studies indicated that the covalently linked quinone moieties bear a large torsional angle. Nevertheless, the reduction potentials rose significantly with the order of monomer < dimer < trimer, indicating that the negative charge was efficiently delocalized within the radical anions.

Emission from Charge Recombination between Radical Cations and Radical Anions of 9‐Cyano‐10‐(p‐Substituted Phenyl)Anthracene Generated during Pulse Radiolysis

AbstractEmission from charge recombination between radical cations and anions of 9‐cyano‐10‐(p‐substituted phenyl)anthracenes (RA, where R is 10‐p‐substituted phenyl: R = Phenyl (PA), anisyl (OA), p‐N,N‐dimethylaminophenyl (NA), N, N‐di‐p‐anisylaminophenyl (DA)), as donor‐acceptor type molecules, generated during the pulse radiolysis in benzene was measured together with the transient absorption of RA radical cations (RA•+) and anions (RA•−). Based on the transient absorption and density functional theory (DFT‐B3LYP/6‐31G*) calculation, a twisted geometry is assumed for all RA in the ground state, RA•+, and RA•−. It is suggested that the positive charge of PA•+, OA•+, and NA•+ is delocalized on two moieties, and that of DA•+ is localized on the donor N,N‐di‐p‐anisylaminophenyl moiety, while the negative charge of all RA•− is mainly on the acceptor 9‐(10‐cyano)anthracenyl moiety. When both RA•+ and RA•− are generated with sufficiently high concentrations during the pulse radiolysis in benzene, the charge recombination between RA•+ and RA•− occurred to give RA in the singlet excited state (1RA*) as the emissive species, but not the excimers because of the twisted geometries of RA•+ and RA•− with the large torsional angles between the 9‐(10‐cyano)anthracenyl and p‐substituted phenyl moieties. Not only the fluorescence quantum yield of 1RA* but also the energy differences between the annihilation enthalpy change and the excitation energy of 1RA* are important factors for the radiolysis induced emission intensity of RA in benzene.

Phenylthiophene−Dipicolinic Acid-Based Emitters with Strong Solution Blue and Solid State Green Emission

The synthesis and characterization of highly efficient blue emitting phenyl-thiophene compounds derivatized with dipicolinic acid bis(diethylamide) and dipicolinic acid diethyl ester 1, 2, and 3 are reported. Quantum yields were determined to be between 97% and 76% in methanol and 99% and 49% in toluene solution. The solvent dependences of the solution luminescence behavior are discussed in terms of solvent refractive index and dielectric constant as well as hydrogen-bonding capability. Luminescence is also observed in the solid state for the three compounds. A bathochromic shift in the emission wavelength is accompanied by solid-state quantum yields between 29% and 4%. HOMO and LUMO energies, in the range -5.55 to -5.71 eV and -2.20 to -2.48 eV, respectively, were determined experimentally from cyclic voltammetry and absorption spectroscopy experiments. The electrochemical characterization revealed that cyclic voltammetry can be utilized to deposit thin films of 3. An X-ray quality single crystal of 1 was isolated. This compound crystallizes in the monoclinic space group P21/c with cell parameters a = 15.224(3) A, b = 8.9383(18) A, c = 17.234(3) A, beta =114.36(3) degrees, and V = 2136.4(7) A3. Appreciable solid state interactions in the form of pi-pi or S-S short contacts are not present, only weaker C-H...pi. A large torsion angle of 30.28 degrees between the phenyl and thiophene moieties and a small torsion angle of -3.37 degrees between the pyridine and the thiophene moieties are seen.

Magnetic interactions in p-phenylene-bis(nitronyl nitroxide) biradicals with large torsion angles

We have designed and synthesized new biradicals of p-phenylene-bis(nitronyl nitroxide) substituted with two methoxy groups at 2,3- ( 2) and 2,5-positions ( 3). A parent biradical p-phenylene-bis(nitronyl nitroxide) ( 1) has intramolecular antiferromagnetic exchange interaction of 2 J/ k B = −104 K ∼ −106 K with a torsion angle of 28.5° between the phenyl and the imidazole rings of nitronyl nitroxide. X-ray crystal structure analysis shows that the bulky substituents in 2 and 3 give large torsion angles of 65–70°. The larger torsion angles should weaken the magnitude of intramolecular exchange interactions, which is attributed to a decrease in π-conjugation over the p-phenylene and the radical groups. Magnetic susceptibility measurements indicate that the intramolecular exchange interactions in 2 and 3 are severely weakened to about 6% of that in 1, 2 J/ k B = −6 K ∼ −8 K. The relation between the torsion angle and the intramolecular exchange interaction is consistent with DFT calculations. The ground-state singlet biradicals with suppressed intramolecular exchange interactions can be a building block for exotic exchange-coupled spin systems as predicted in our theoretical studies.

Internal rotation and hyperfine coupling interaction in deuterated acetaldehyde

Theoretical and experimental investigations of the hyperfine structure of deuterated acetaldehyde (CD 3COH) are presented. The theoretical approach accounts for the large amplitude internal rotation of the CD 3 group. A hyperfine Hamiltonian, depending on the large amplitude torsional angle, is written taking into account quadrupole hyperfine coupling arising from the three deuterium atoms. Effective hyperfine coupling Hamiltonians are derived for A- and E-type rotation–torsion levels. In the former case, a very symmetrical operator arises in which the hyperfine coupling is the same for all three deuterium atoms. In the latter case the operators are less symmetrical. Hyperfine levels are calculated using symmetry adapted hyperfine wavefunctions in order to build total hyperfine-rotation–torsion wavefunctions satisfying the Pauli exclusion principle. The theoretical approach is used to carry out analyses of six hyperfine patterns which were recorded using a pulsed molecular beam Fourier transform microwave spectrometer. The experimental resolution of this apparatus allows us to resolve individual hyperfine components in many cases. The results of the analysis are consistent with deuterium atoms having an effective quadrupole coupling tensor which, except for appropriate rotations, is quite close to that in CH 3D.

The Combi-Targeting Concept: Synthesis of Stable Nitrosoureas Designed to Inhibit the Epidermal Growth Factor Receptor (EGFR)

According to the "combi-targeting" concept, the EGFR tyrosine kinase (TK) inhibitory potency of compounds termed "combi-molecules" is critical for selective growth inhibition of tumor cells with disordered expression of EGFR or its closest family member erbB2. Here we report on the optimization of the EGFR TK inhibitory potency of the combi-molecules of the nitrosourea class by comparison with their aminoquinazoline and ureidoquinazoline precursors. This led to the discovery of a new structural parameter that influences their EGFR TK inhibitory potency, i.e., the torsion angle between the plane of the quinazoline ring and the ureido or the nitrosoureido moiety of the synthesized drugs. Compounds (3'-Cl and Br series) with small angles (0.5-3 degrees ) were generally stronger EGFR TK inhibitors than those with large angles (18-21 degrees ). This was further corroborated by ligand-receptor van der Waals interaction calculations that showed significant binding hindrance imposed by large torsion angles in the narrow ATP cleft of EGFR. Selective antiproliferative studies in a pair of mouse fibroblast NIH3T3 cells, one of which NIH3T3/neu being transfected with the erbB2 oncogene, showed that IC(50) values for inhibition of EGFR TK could be good predictors of their selective potency against the serum-stimulated growth of the erbB2-tranfected cell line (Pearson r = 0.8). On the basis of stability (t(1/2)), EGFR TK inhibitory potency (IC(50)), and selective erbB2 targeting, compound 23, a stable nitrosourea, was considered to have the structural requirements for further development.

Polymorphism of 2,5-Diphenyl-1,4-distyrylbenzene with Two cis Double Bonds: The Essential Role of Aromatic CH/π Hydrogen Bonds

Three polymorphs of 2,5-diphenyl-1,4-distyrylbenzene with two cis double bonds (cis-DPDSB) have been prepared by altering the crystal growth conditions. The crystal data reveal that there are in total four crystallographically independent conformations of the molecule in the three polymorphs and the backbone of cis-DPDSB largely deviates from a plane with large torsion angles in each conformation. For the three-dimensional conformations of the molecules, there is no face-to-face stacking in all polymorphs. The aromatic CH/π hydrogen bonds, which are identified as the main driving force for the crystal packing with interaction distances about 2.7−3.1 A, are the origin of the variable conformations and polymorphic formations during the crystal growth processes. Temperature-dependent IR spectra have shown that the intermolecular aromatic CH/π hydrogen bonds influence the aromatic C−H vibrations, and the interactions become slightly decoupled when the temperature is elevated.

Phthalazine PDE IV inhibitors: Conformational study of some 6-methoxy-1,4-disubstituted derivatives

This report describes the detailed conformational analysis and synthesis of a series of phthalazine phosphodiesterase-type (IV) (PDE IV) inhibitors bearing either mono- or dichloro 4-methylenepyridine at the ‘down’ position of the phthalazine nucleus or different heterocycles at the ‘top’ position 4 of the phthalazine moiety. Both the mono- and dichloro 4-methylenepyridine units linked at carbon C1 of the phthalazine nucleus show identical conformational behaviour with the substituent preferentially oriented towards the external part of the molecule and the pyridine plane almost orthogonal to that of phthalazine ring. The heterocyclic five-membered rings linked at carbon C4 of phthalazine show quite different conformational behaviour. The 1,3-thiazole ring exists in a well-defined conformation almost coplanar with respect to the phthalazine nucleus while the 1,2,4-triazole and the 1,3-diazole heterocycles show a great conformational freedom with large torsion angles. Compound 3 bearing the thiazole ring at C4 displays the major biological activity, thus suggesting that a planar and rather rigid conformation of the pentacycle should favour the PDE IV inhibition capacity of this class of compounds.

2,6-Bis(4-nitrobenzylidene)cyclohexanone

In the crystal structure of the title compound, C20H16N2O5, the cyclo­hexane ring assumes the sofa conformation. Steric repulsions between one of the ortho-H atoms of each of the aryl groups and the equatorial H atoms at positions 3 and 5 of the cyclo­hexane ring lead to large torsion angles between the aryl rings and the adjacent olefinic linkages. Various bond angles confirm this steric impedance between the aryl and cyclo­hexane rings.

Conformational flexibility of antifungal atropisomeric strobilurin analogues: a quantum mechanical investigation

Quantum mechanical calculations were performed on novel N-phenyl-triazolone inhibitors of the mitochondrial bc1 complex. Both conformational flexibility and rotational barrier were examined. For all of the triazolones investigated, there is generally a large inter-ring torsion angle. The rotational barrier varies considerably among these analogues. For example, when a 6-methyl group is substituted on the phenyl ring at a position ortho to the triazolone, the calculated barrier is large enough to allow atropisomers to be stable even at room temperature. The calculated results are in agreement with experimental studies.

Synthesis, Structure, and Properties of [Pt(II)(diimine)(dithiolate)] Dyes with 3,3‘-, 4,4‘-, and 5,5‘-Disubstituted Bipyridyl: Applications in Dye-Sensitized Solar Cells

A family of [Pt(II)(diimine)(dithiolate)] complexes of general formula [Pt{X,X'(CO(2)R)(2)-2,2'-bipyridyl}(maleonitriledithiolate)] (where X = 3, 4, or 5 and R = H or Et) have been synthesized, spectroscopically and electrochemically characterized, and attached to a TiO(2) substrate to be tested as solar cell sensitizers. A single-crystal X-ray structure showing a large torsion angle between the bipyridyl rings was determined for [Pt{3,3'(CO(2)Et)(2)-2,2'-bipyridyl}(maleonitriledithiolate)].MeCN. The effect of changing the position of the bipyridyl substituents from 3,3' to 4,4' and 5,5' is discussed with reference to structural and electronic changes seen within the different members of the family of molecules. The first UV/vis/NIR spectroelectrochemical study of complexes of this general formula is discussed. All three complexes (where R = H) were tested as solar cell sensitizers, with the 3,3'-disubstituted bipyridyl complex giving an intermediate dye loading value but superior photovoltaic performance to those of the other two. The performance of this sensitizer is then compared with that of a well-known Ru polypyridyl sensitizer, the ditetrabutylammonium salt of [RuL(2)(NCS)(2)] (L = 2,2'-bipyridyl-4,4'-dicarboxylato), commonly called N719.

Poly(p-phenylenevinylene) Derivatives Containing Electron-Transporting Aromatic Triazole or Oxadiazole Segments

We report the synthesis, optical and electrochemical details, and properties of copolymers P1−P3 consisting of alternate hole-transporting 1,4-bis(hexyloxy)-2,5-distyrylbenzene (HDB) and electron-transporting 4-(4-(hexyloxy)phenyl)-3,5-diphenyl- 4H-1,2,4-triazole (EDT) or 2,5-diphenyl-1,3,4-oxadiazole (EDO) segments linked via an ether spacer or a twisted σ-bond (biphenyl). These copolymers are soluble in common organic solvents such as chloroform, NMP, and 1,1,2,2-tetrachloroethane and exhibit good thermal stability with decomposition temperatures higher than 375 °C. P1−P3 show efficient energy transfer from EDT or EDO to EDO fluorophores when photoexcited. Optical and electrochemical properties of P1−P3 are also investigated in detail by comparing with P4 and P5 containing similar chromophores. From the cyclic voltammograms the onset oxidation and reduction potentials for isolated P1 and conjugated P2 are comparable, indicating that the effect of the twisted σ-bond in P2 is similar to that of the ether spacer in P1. The optimized geometries of P2 and P3 show that the torsion angle between HDB and EDT or EDO are 83.6° or 89.6°, respectively, based on MNDO semiempirical calculations. The large torsion angle in P2 and P3 significantly limits delocalization of charges between hole- and electron-transporting segments. Accordingly, in P2 and P3 the oxidation and reduction starts at the hole- and the electron-transporting, respectively, like those in isolated P1. The HOMO and LUMO energy levels of P1, P2, and P3, estimated from electrochemical data, are −5.16, −5.12, and −5.19 eV and −3.35, −3.38, and −3.23 eV, respectively. Single-layer light-emitting diodes (Al/P1−P3/ITO) have been successfully fabricated, and they reveal blue or yellow electroluminescence.

Oligomers of Hexa-peri-hexabenzocoronenes as “Super-oligophenylenes”: Synthesis, Electronic Properties, and Self-assembly

Hexa-peri-hexabenzocoronene (HBC) is a remarkable polycyclic aromatic hydrocarbon and is often called "superbenzene" because of its similarity to benzene. In this article we present the facile synthesis of oligomers of HBC, up to trimers (3, 4, 5a-c) with different modes of connection. UV-vis and fluorescence spectroscopy studies reveal that the oligomers are electronically decoupled. This arises from the small atomic orbital coefficients of the bridge-head carbon atoms, the large torsion angle between the HBC units, and the large distance of interacting transition dipoles due to the size of the HBC chromophore. For comparison, a methylene-bridged HBC dimer 6, so-called "superfluorene", was prepared. The induced planarity improves pi-conjugation and suppresses the geometrical relaxation of the backbone upon electronic excitation, leading to a prominent 0-0 transition band in the fluorescence spectra. The self-assembly of the oligomers and of superfluorene 6 was studied by wide-angle X-ray diffraction (WAXD) in the bulk state, and ordered columnar stacking occurs in the HBC dimer 3, p-HBC trimer 4, and superfluorene 6. Measurements of shear-aligned samples show that, despite increasing aspects ratio by linear entrainment of disks, the anitropic element that is subject to alignment by shear is the supramolecular columns.

Antiferromagnetic exchange in meta-phenylene bridged bis(tris-o-iminosemiquinonato)metal complexes

By reaction of the ligand N,N′ bis(3,5-di-tert-butyl-2-hydroxyphenyl)-1,3-phenylenediamine (1), with Fe, Co or Mn salts, three complexes were synthesized where the bis-bidentate ligand is in the bis-semiquinonato oxidation state. Although the m-phenylene linker is known to afford ferromagnetic coupling in diradicals, the antiferromagnetic interaction of intramolecular origin we observed is not unexpected, given the large torsion angles between the semiquinonato and the m-phenylene planes.