Triangular Complex Research Articles

Pathway selection in the self-assembly of Rh4L4 coordination squares under kinetic control

Pathway selection principles in reversible reaction networks such as molecular self-assembly have not been established yet, because achieving kinetic control in reversible reaction networks is more complicated than in irreversible ones. In this study, we discovered that coordination squares consisting of cis-protected dinuclear rhodium(II) corner complexes and linear ditopic ligands are assembled under kinetic control, perfectly preventing the corresponding triangles, by modulating their energy landscapes with a weak monotopic carboxylate ligand (2,6-dichlorobenzoate: dcb–) as the leaving ligand. Experimental and numerical approaches revealed the self-assembly pathway where the cyclization step to form the triangular complex is blocked by dcb–. It was also found that one of the molecular squares assembled into a dimeric structure owing to the solvophobic effect, which was characterized by nuclear magnetic resonance spectroscopy and single-crystal X-ray analysis.

Matrices whose powers are eventually triangular

Square matrices whose powers eventually have some special properties are of both theoretical significance and application value. This paper investigates those complex matrices whose powers are eventually triangular. We completely characterize the eventually triangular complex matrices of order not greater than 4, and extend the results to the nonnegative case. Eventually triangular matrices of order n are also discussed.

Numerical computation of triangular complex spherical designs with small mesh ratio

This paper provides triangular spherical designs for the complex unit sphere Ωd⊂ℂd by exploiting the natural correspondence with the real unit sphere S2d−1⊂R2d. A variational characterization of triangular complex designs is provided, with particular emphasis on numerical computation of efficient triangular complex designs with good geometric properties as measured by their mesh ratio. We give numerical examples of triangular spherical t-designs on complex unit spheres of dimension d=2 to 6.

Controlling Cation Distribution and Morphology in Colloidal Zinc Ferrite Nanocrystals.

This paper describes the first synthetic method to achieve independent control over both the cation distribution (quantified by the inversion parameter x) and size of colloidal ZnFe2O4 nanocrystals. Use of a heterobimetallic triangular complex of formula ZnFe2(μ3-O)(μ2-O2CCF3)6(H2O)3 as a single-source precursor, solvothermal reaction conditions, absence of hydroxyl groups from the reaction solvent, and the presence of oleylamine are required to achieve well-defined, crystalline, and monodisperse ZnFe2O4 nanoparticles. The size of the ZnFe2O4 nanocrystals increases as the ratio of oleic acid and oleylamine ligands to precursor increases. The inversion parameter increases with increasing solubility of the precursor in the reaction solvent, with the presence of oleic acid in the reaction mixture, and with decreasing reaction temperature. These results are consistent with a mechanism in which ligand exchange between oleic acid and carboxylate ligands bound to the precursor complex influences the degree to which the reaction produces a kinetically trapped or thermodynamically stable cation distribution. Importantly, these results indicate that preservation of the triangular Zn–O–Fe2 core structure of the precursor in the reactive monomer species is crucial to the production of a phase-pure ZnFe2O4 product and to the ability to tune the cation distribution. Overall, these results demonstrate the advantages of using a single-source precursor and solvothermal reaction conditions to achieve synthetic control over the structure of ternary spinel ferrite nanocrystals.

Antisymmetric Exchange in a Real Copper Triangular Complex

The antisymmetric exchange, also known as the Dzyaloshinskii-Moriya interaction (DMI), is an effective interaction that may be at play in isolated complexes (with transition metals or lanthanides, for instance), nanoparticles, and highly correlated materials with adequate symmetry properties. While many theoretical works have been devoted to the analysis of single-ion zero-field splitting and to a lesser extent to symmetric exchange, only a few ab initio studies deal with the DMI. Actually, it originates from a subtle interplay between weak electronic interactions and spin-orbit couplings. This article aims to highlight the origin of this interaction from theoretical grounds in a real tri-copper(II) complex, capitalizing on previous methodological studies on bi-copper(II) model complexes. By tackling this three-magnetic-center system, we will first show that the multispin model Hamiltonian is appropriate for trinuclear (and likely for higher nuclearity) complexes, then that the correct application of the permutation relationship is necessary to explain the outcomes of the ab initio calculations, and finally, that the model parameters extracted from a binuclear model transfer well to the trinuclear complex. For a more theory-oriented purpose, we will show that the use of a simplified structural model allows one to perform more demanding electronic structure calculations. On this simpler system, we will first check that the previous transferability is still valid, prior to performing more advanced calculations on the derived two-magnetic-center model system. To this end, we will explain in detail the physics of the DMI in the copper triangle of interest, before advocating further theory/experiment efforts.

Dynamic Au-C σ-Bonds Leading to an Efficient Synthesis of [n]Cycloparaphenylenes (n = 9-15) by Self-Assembly.

The transmetalation of the digold(I) complex [Au2Cl2(dcpm)] (1) (dcpm = bis(dicyclohexylphosphino)methane) with oligophenylene diboronic acids gave the triangular macrocyclic complexes [Au2(C6H4)x(dcpm)]3 (x = 3, 4, 5) with yields of over 70%. On the other hand, when the other digold(I) complex [Au2Cl2(dppm)] (1′) (dppm = bis(diphenylphosphino)methane) was used, only a negligible amount of the triangular complex was obtained. The control experiments revealed that the dcpm ligand accelerated an intermolecular Au(I)–C σ-bond-exchange reaction and that this high reversibility is the origin of the selective formation of the triangular complexes. Structural analyses and theoretical calculations indicate that the dcpm ligand increases the electrophilicity of the Au atom in the complex, thus facilitating the exchange reaction, although the cyclohexyl group is an electron-donating group. Furthermore, the oxidative chlorination of the macrocyclic gold complexes afforded a series of [n]cycloparaphenylenes (n = 9, 12, 15) in 78–88% isolated yields. The reorganization of two different macrocyclic Au complexes gave a mixture of macrocyclic complexes incorporating different oligophenylene linkers, from which a mixture of [n]cycloparaphenylenes with various numbers of phenylene units was obtained in good yields.

Clique dynamics of locally cyclic graphs with δ ≥ 6

We prove that the clique graph operator k is divergent on a locally cyclic graph G (i.e. NG(v) is a circle) with minimum degree δ(G)=6 if and only if G is 6-regular. The clique graph kG of a graph G has the maximal complete subgraphs of G as vertices, and the edges are given by non-empty intersections. If all iterated clique graphs of G are pairwise non-isomorphic, the graph G is k-divergent; otherwise, it is k-convergent.To prove our claim, we explicitly construct the iterated clique graphs of those infinite locally cyclic graphs with δ≥6 which induce simply connected simplicial surfaces. These graphs are k-convergent if the size of triangular-shaped subgraphs of a specific type is bounded from above. We apply this criterion by using the universal cover of the triangular complex of an arbitrary finite locally cyclic graph with δ=6, which shows our divergence characterisation.

Strongly Ad‐Nilpotent Elements of the Lie Algebra of Upper Triangular Matrices

In this paper, the strongly ad‐nilpotent elements of the Lie algebra of upper triangular complex matrices are studied. We prove that all the nilpotent matrices in are strongly ad‐nilpotent if and only if n ≤ 6. Additionally, we prove that all the elements exp(ad x), x strongly ad‐nilpotent generate the inner automorphism group Int t(n, ℂ).

Effect of the Additional Carboxyl Group in Half‐Sandwich Organometallic 2,4‐Dipicolinate Complexes on Solution Speciation and Structure

AbstractSolution speciation of Rh(η5‐C5Me5), Ru(η6‐p‐cymene) and Ru(η6‐toluene) complexes of 2,4‐pyridinedicarboxylic acid (2,4‐dipicH2) was studied and compared to that of 2‐picolinic acid (picH) in addition to their reactivity towards chloride and bromide ions, 1‐methylimidazole and guanosine. Structures of [Rh(η5‐C5Me5)(2,4‐dipicH)Cl] ⋅ 3H2O (1), 2[Ru(η6‐toluene)(2,4‐dipicH)Cl] ⋅ 3H2O (2) and [Ru(η6‐toluene)(2,4‐dipic)]3 ⋅ 7H2O (3) were analyzed by X‐ray diffraction. 1 and 2 show typical piano stool geometry, while 3 is a triangular complex stabilized via the monodentate coordination of the second carboxylate group to the neighboring Ru(II) center. High stability [M(arene)L(H2O/Cl)] species predominate at pH 7.4. 2,4‐Dipic forms more stable complexes with Ru(η6‐arene) than pic, with this difference being minor in the case of the Rh(η5‐C5Me5) complexes. A lower affinity of 2,4‐dipic complexes to halide ions was found compared to the corresponding pic complexes due to the additional COO− moiety.

A hybrid bioinspired catechol-alloxazine triangular nickel complex stabilizing protons and electrons

A new class of redox-active ligands merging catechol and alloxazine structures is reported. A trimetallic triangular complex is formed upon complexation to nickel.

Removal of boron and silicon by a modified resin and their competitive adsorption mechanisms

Boron and silicon are essential trace elements for living organisms. However, these are undesirable in excess amounts owing to the toxic effects of boron on plants, animals, and humans, and the silica scale formation by silicon in water treatment processes. Herein, a new diol-type adsorbent (T-resin) was synthesized by grafting tiron (disodium 4,5-dihydroxy-1,3-benzenedisulfonate) onto an ion-exchange resin (grafting amount is 1.2mmol/gdry) to separate boron and silicon from a solution. The effects of pH, initial concentration, and coexisting anions, particularly, the effect of the coexistence of silicate ion on the adsorption of boron, were investigated. T-resin showed good adsorption properties for both boron and silicon in a wide pH range (pH2-10). The adsorption of boron and silicon was effectively described by the Langmuir isotherm, and the maximum adsorption capacities of boron and silicon were 21.25mg/g and 8.36mg/g, respectively. In a competitive adsorption system, boron and silicon were simultaneously adsorbed on the T-resin, but the adsorption rate of boron was faster than silicon. However, silicon could replace the boron adsorbed on the resin, indicating that the adsorption of silicon was more stable than boron. 11B and 29Si solid state NMR data confirmed the different adsorption mechanisms of the two elements. Boron was adsorbed via two types of complexes, a triangular complex of [LB(OH)], as well as 1:1 tetrahedral complex of [LB(OH)2] and 1:2 tetrahedral complex of [BL2], whereas silicon was only adsorbed via a 1:3 octahedral complex of [SiL3]. Graphical abstract A new diol-type absorbent was synthesized by grafting tiron onto an ion-exchange resin to separate boron and silicon from a solution. Boron and silicon competitively adsorbed on the T-resin, and silicon could replace the boron adsorbed on the resin. 11B and 29Si solid state NMR data confirmed the different adsorption mechanisms of the two elements. Boron was adsorbed via two types of complexes, a triangular complex of [LB(OH)], as well as 1:1 tetrahedral complex of [LB(OH)2] and 1: 2 tetrahedral complex of [BL2], whereas silicon was only adsorbed via a 1:3 octahedral complex of [SiL3].

Réinsertion fovéale du complexe triangulaire fibro-cartilagineux purement arthroscopique. Description technique et résultats préliminaires

Foveal attachment of the triangular fibrocartilaginous complex (TFCC) is essential for distal radioulnar joint stability. Controversy still exists as to which is the best treatment in case of foveal lesions. Actual arthroscopic techniques either require mini open steps or are complex and expensive. We present a simple all inside knotless repair providing a strong bony fixation in the fovea. Between 2013 and 2016, a cohort of 5 patients presenting with isolated Palmer 1B, EWAS 2 lesions of the TFCC were operated on with this technique. Clinical evaluations were based on a compared measurement of the grip strength, pain on a visual analogic scale, of the different ranges of motion and distal radioulnar joint (DRUJ) stability. We also used functional scores : Mayo Modified Wrist Score (MMWS), Quick DASH (Disability Arm, shoulder and Hand) and PRWE. The average follow-up was 29.4 months (range 9 to 42 months). Through 3-4 and 6R portals, the ulnar fovea is debrided and a wire is passed percutaneously through the TFCC to place a mattress suture on its free end. It is then reattached to the fovea with an impacted anchor. On postoperative evaluation, pain was reduced of 5 points (range 1 to 9), grip strength averaged 94% of the unaffected side. Range of motion averaged 92% of the unaffected side. DRUJ instability was slight in 4 patients and mild in 1 patient. MMWS was excellent for 1, good for 1 and satisfactory for 3 patients. Quick Dash averaged 17,68 (range 0 to 38.6) compared to preoperative average of 59.48 (range 45 to 77) with an amelioration of 43 (range 34 to 57). PRWE averaged 20 (range 1 to 41.5) compared to preoperative average of 60.3 (range 33.5 to 76.5) with an amelioration of 41 (range 32 to 58). We reported no complications and particularly no lesions of the dorsal sensory branch of the ulnar nerve. Repairs performed with this technique are simple and results achieved seems to be similar to those obtained with conventional open or arthroscopic techniques, although further investigation with an increased number of patients and follow-up are required. We present a simple arthroscopic technique using a single suture anchor placed in the ulnar fovea, which became our first choice of treatment in EWAS 2 lesions of the TFCC.

Réinsertion fovéale du complexe triangulaire fibrocartilagineux purement arthroscopique. Desciption technique et résultats préliminaires

Introduction Foveal attachment of the triangular fibrocartilaginous complex (TFCC) is essential for distal radioulnar joint stability. Controversy still exists as to which is the best treatment in case of foveal lesions. Actual arthroscopic techniques either require mini open steps or are complex and expensive. We present a simple all inside knotless repair providing a strong bony fixation in the fovea. Material and method Operative Techniques: Through 3–4 and 6R portals, the ulnar fovea is debrided and a wire is passed percutaneously through the TFCC to place a mattress suture on its free end. It is then reattached to the fovea with an impacted anchor. Retrospective study Between 2013 and 2016, a cohort of 5 patients presenting with isolated Palmer 1B, EWAS 2 lesions of the TFCC were operated on with this technique. Clinical evaluations were based on a compared measurement of the grip strength, pain on a visual analogic scale, of the different ranges of motion and distal radioulnar joint (DRUJ) stability. We also used functional scores: Mayo Modified Wrist Score (MMWS), Quick DASH (Disability Arm, shoulder and Hand) and PRWE. The average follow up was 29,4 months (range 9 to 42 months). Results On postoperative evaluation, pain was reduced of 5 points (range 1 to 9), grip strength averaged 94 % of the unaffected side. Range of motion averaged 92 % of the unaffected side. DRUJ instability was slight in 4 patients and mild in 1 patient. MMWS was excellent for 1, good for 1 and satisfactory for 3 patients. Quick Dash averaged 17.68 (range 0 to 38.6) compared to preoperative average of 59.48 (range 45 to 77) with an amelioration of 43 (range 34 to 57). PRWE averaged 20 (range 1 to 41.5) compared to preoperative average of 60.3 (range 33.5 to 76.5) with an amelioration of 41 (range 32 to 58). We reported no complications and particularly no lesions of the dorsal sensory branch of the ulnar nerve. Conclusions We present a simple arthroscopic technique using a single suture anchor placed in the ulnar fovea. Repairs performed in this fashion are simple and results achieved seems to be similar to those obtained with conventional open or arthroscopic techniques, although further investigation with an increased number of patients and follow up are required. It however became our first choice of treatment in EWAS 2 lesions of the TFCC.

Mononuclear and trinuclear DyIII SMMs with Schiff-base ligands modified by nitro-groups: first triangular complex with a N-N pathway.

Using two Schiff-base ligands containing an electron-withdrawing group (NO2), we obtained two mononuclear and two trinuclear complexes with the general formula [Dy(hni)(NO3)(DMF)2]·DMF (1·DMF), [Dy(hni)2(H2O)2]·NO3·EtOH (2·NO3·EtOH), [Dy3(hnc)3(DMF)6] (3) and [Gd3(hnc)3(DMF)6] (4) (H-hni: 2-(hydroxyl-3-methoxy-5-nitrophenyl)methylene(isonictino)hydrazine and H3-hnc: 1,5-bis(2-hydroxy-3-methoxy-5-nitrobenzylidene)carbonohydrazide). Four complexes were confirmed by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure of complex 3 reveals that the modified Schiff-base ligand provides two different tridentate coordination pockets (ONN and ONO) to encapsulate DyIII with a unique N-N pathway. The magnetic properties of all four complexes have been investigated using dc and ac susceptibility measurements. The frequency-dependent ac susceptibility is indicative of single-molecule magnetic behavior without and/or with an optimum dc field with a relaxation barrier Ueff = 34 K (400 Oe), 19 K (0 Oe) and 80 K (0 Oe) for complexes 1, 2 and 3, respectively.

Pair-delocalization in trigonal mixed-valence clusters: new insight into the vibronic origin of broken-symmetry ground states.

A new vibronic mechanism for the stabilization of pair-delocalized electronic states in trigonal trimeric mixed valence complexes (such as iron-sulfur [Fe3S4]0 proteins) is proposed. Unlike the previously reported mechanism based on the Piepho-Krausz-Schatz model dealing with the local "breathing" vibrations, the present mechanism involves the multicenter vibrations of the triangular complex, which change the metal-metal distances. The former mechanism of the vibronic coupling in combination with the double exchange and Heisenberg type exchange (superexchange) interactions accounts for the existence of the pair-delocalized states of many-electron mixed valence clusters in the intermediate ground spin states. In contrast to the previous model, within which the conditions for the occurrence of pair delocalized states are spin-dependent, the pair delocalization phenomenon in the proposed model is exclusively based on a clear physical mechanism of the interplay between the inter-center vibronic coupling and electron transfer. Therefore, the proposed mechanism demonstrates that the pair delocalization is a more common feature of mixed valence complexes and can appear not only in multi-electron trimers as a result of the interplay between several parameters, but even in one-electron mixed valence trimers in which neither double exchange nor superexchange is operative. The conditions for the pair delocalization in the proposed model are shown to be dependent on the value and sign of the electron transfer parameter as well as on the ratio of the frequencies of the fully symmetric (a1) and doubly degenerate (e) vibrations of a triatomic molecule.

Structural basis for λN-dependent processive transcription antitermination.

λN-mediated processive antitermination constitutes a paradigmatic transcription regulatory event, during which phage protein λN, host factors NusA, NusB, NusE and NusG, and an RNA nut site render elongating RNA polymerase termination-resistant. The structural basis of the process has so far remained elusive. Here we describe a crystal structure of a λN-NusA-NusB-NusE-nut site complex and an electron cryo-microscopic structure of a complete transcription antitermination complex, comprising RNA polymerase, DNA, nut site RNA, all Nus factors and λN, validated by crosslinking/mass spectrometry. Due to intrinsic disorder, λN can act as a multiprotein/RNA interaction hub, which, together with nut site RNA, arranges NusA, NusB and NusE into a triangular complex. This complex docks via the NusA N-terminal domain and the λN C-terminus next to the RNA exit channel on RNA polymerase. Based on the structures, comparative crosslinking analyses and structure-guided mutagenesis, we hypothesize that λN mounts a multipronged strategy to reprogram the transcriptional machinery, which may include (1) the λN C terminus clamping the RNA exit channel, thus stabilizing the DNA:RNA hybrid; (2) repositioning of NusA and RNAP elements, thus redirecting nascent RNA and sequestering the upstream branch of a terminator hairpin; and (3) hindering RNA engagement of termination factor ρ and/or obstructing ρ translocation on the transcript.

El papel de la rehabilitación tras las reparaciones de las inestabilidades de muñeca

One of the most frequent wrist pathologies seen by the hand surgeon are the carpal instabilities together with the pain in the ulnocarpal side. The most common causes are due to injuries in the fibrocartilage triangular complex. These injuries sometimes may cause an instability of the distal radio-ulnar joint. After an analysis of the anatomical and biomechanical data, and taking the few rehabilitation protocols of scapholunate and lunotriquetral instabilities published in the literature, specific rehabilitation programs for each one of these are presented. A description of the protocols is provided for rehabilitation after fibrocartilage triangular complex repairs, as well as of the protocols currently used by us.The importance of the propioceptive re-education in this type of injuries is also defined, and a detailed description of program of gradual introduction to certain exercises aimed at this.

Arthroscopic treatment for ulnar-sided TFCC-tears.

Ruptures of ulnar-sided triangular fibrocartilaginous complex (TFCC) often occur in cases of trauma. Golden standard for diagnosis is the arthroscopy of the wrist. TFCC lesions are classified according to their location if traumatic in origin or if degenerative according to their severity. Recent literature has focused on the ruptures of ulnar-sided triangular fibrocartilaginous complex. This article describes conservative, operative and arthroscopic surgical techniques to reconstruct the triangular fibrocartilaginous complex and restore distal radioulnar joint stability. The main therapeutic goal should be the stabilization of the DRUJ by reattachment of the torn ligaments in ulnar-sided ruptures to the deep fibers in the fovea. This reinsertion can be performed by transosseous suture, a suture anchor or open. Central TFCC tears are typically located close to the sigmoid notch of the radius and are either traumatic or degenerative in origin. While central TFCC lesions are usually treated by arthroscopic debridement using small joint punches or a bipolar high frequency system, the ulnar TFCC avulsions can also be refixed arthroscopically in different techniques.

La prise en charge des lésions du TFCC chez les adolescents par arthroscopie et mini voie d’abord

Purpose Post-traumatic injury of the triangular fibrocartilagineus complex (TFCC) can result in debilitating wrist problems. Although diagnosis and treatment of these lesions is well described for the adult population, hardly any data exists for this type of injury in young adolescents. Methods Between 2011 and 2014 seven patients between 10 and 14 years of age have consulted our department for posttraumatic ulnar-sided wrist pain. Previous trauma included distal radial fractures with a concomitant fracture of the ulnar styloid, multiple micro-traumas of the wrist and an overuse injury. Clinical evaluation showed tenderness over the TFCC complex, pain on movement and in most cases instability of the distal radio-ulnar joint (DRUJ) with episodes of sub/dislocation in two patients. Pre-operative arthro-MRIs were conducted confirming the pathology in only 3 cases. Therefore, all patients underwent diagnostic arthroscopy of the wrist followed by surgical treatment according to the discovered lesion. The mean age at the time of surgery was 12.9 years. Results Arthroscopy of the wrist confirmed a TFCC lesion in all patients. In 5 cases the injury was classified as Palmer type 1B, once as a combined type 1A/1B and once as type 1A. All 6 patients with a type 1B injury underwent arthroscopically assisted mini-open reconstruction of the TFCC. Treatment of the type 1A injury consisted of arthroscopic shaving of the central lesion. Postoperative clinical examination revealed stable wrists with a normal range of motion in all cases. Patients reported a decrease in pain-level during daily activities or were entirely pain-free. Conclusion TFCC lesions in the adolescent population are difficult to evaluate on an arthro-MRI and results are often inconclusive. Diagnostic arthroscopy is thus the preferred method of diagnosis for this type of injury. The arthroscopic assisted mini-open TFCC reconstruction is a reliable technique to achieve DRUJ stability and good clinical outcomes.

Modified oblique ulnar shortening osteotomy combined with arthroscopic synovectomy for treatment of ulnar impingement syndrome

Objective To introduce a modified oblique ulnar shortening technique combined with arthroscopic synovectomy for treating ulnar impingement syndrome without the Rayhack system,and to evaluate the outcomes.Methods From March 2010 to July 2013,11 cases of ulnar positive variance with consistent ulnar wrist pain were treated with oblique osteotomy of the ulna and intemal fixation with a volar Zimmer compression plate.Arthroscopic debridement of the triangular fibrous cartilage complex (TFCC) was also done simultaneously.Postoperatively bone union,wrist pain and wrist function were followed.Results All the cases were follow-up for 6 to 24 months,with an average of 14 months.Average bone union time was 10 weeks.There was no non-union.Postoperative VAS for pain dropped from 5.6 to 1.2.According to Modified Mayo wrist score,the wrist function was excellent in 6 cases,good in 4 cases and fair in 1 case.Wrist range of motion and grip strength recovered well.All the patients went back to previous work in 3 months.Conclusion The modified oblique osteotomy with volar compression plate and lag screw fixation for ulnar shortening combined with arthroscopic synovectomy is an effective treatment for ulnar impingement syndrome.It decreases the incidence of bone nonunion and dorsal implant protruding. Key words: Arthroscopes; Surgical procedures, operative ; Ulnar impingement syndrome; Ulnar shortening