Selective Construction of Molecular Borromean Rings and [2]Catenane Utilizing Ether Bipyridyl Ligands.

A series of Cp* Rh-based discrete architectures was constructed by selecting four ether bipyridyl ligands and three half-sandwich rhodium(III) bimetallic construction units, respectively. This study demonstrates a strategy for making the transition from a binuclear D-shaped ring to a tetranuclear [2]catenane by adjusting the length of bipyridyl ligands. In addition, changing the position on the naphthyl group of the bipyridyl ligand from 2,6- to 1,5-position substitution can realize the selective synthesis of [2]catenane and Borromean rings under similar conditions. The above-mentioned constructions have been determined via X-ray crystallographic analysis, detailed NMR techniques, electrospray ionization-time-of-flight/mass spectrometry analysis, and elemental analysis.

Organometallic Borromean Rings and [2]Catenanes Featuring Di-NHC Ligands.

We report herein a series of organometallic Borromean rings (BRs) and [2]catenanes prepared from benzobiscarbene ligands. The reaction of dinickel complexes of the benzobiscarbenes 1 a-1 c with a thiazolothiazole bridged bipyridyl ligand L2 led by self-assembly to a series of organometallic BRs. Solvophobic effects played a crucial role in the formation and stability of the interlocked species. The stability of BRs is related to the N-alkyl substituents at the precursors 1 a-1 c, where longer alkyl substitutes improve stability and inter-ring interactions. Solvophobic effects are also important for the stability of [2]catenanes prepared from 1 a-1 c and a flexible bipyridyl ligand L3 . In solution, an equilibrium between the [2]catenanes and their macrocyclic building blocks was observed. High proportions of [2]catenanes were obtained in concentrated solutions or polar solvents. The proportion of [2]catenanes in solution could be further enhanced by lengthening of the N-alkyl substitutes.

Rational Construction of Borromean Linked Crystalline Organic Polymers.

Attributed to the unique topological complexity and elegant beauty, Borromean systems are attracting intense attention. However, at present, the construction of Borromean linked organic polymers remains a challenge. To address this formidable challenge, we developed a supramolecular-synthon-driven approach to fabricate Borromean linked organic polymer. The solvothermal condensation reaction of a judiciously selected trigonal pyramidal building block, 1,3,5-Tris(4-aminophenyl)adamantane, with linear dialdehyde building blocks allowed the construction of two rare covalent organic frameworks (COFs) with high crystallinity and robustness. Structure refinement unveiled the successful formation of entangled 2D→2D Borromean arrayed structures. Both the two COFs were of microporosity and thus demonstrated the potentials for gas separation. The successful synthesis of the first two Borromean linked organic polymers paves the avenue to expand the supramolecular-synthon-driven approach to other building blocks and topologies, and broadens the family and scope of COFs.

Self-assembly of molecular Borromean rings from bimetallic coordination rectangles.

In contrast to conventional stepwise synthesis of molecular Borromean rings, a self-assembly synthetic method which proceeds without the aid of a template has been developed. In the formation of molecular rectangles, by adjustment of the long-arm length of the rectangles, a series of size-dependent Borromean-link frameworks were constructed. Both the shortest length of two arms and the relative proportion of the length of the long arm to that of the short arm play a key role in the formation of Borromean rings. DFT calculations were used to provide theoretical support for the formation of discrete interlocked frameworks.

Using Rigidity and Conjugation of Subunits to Modulate Supramolecular Topologies Constructed by Half-Sandwich Fragments.

The synthesis of supramolecular compounds with a high degree of controllability and the targeted modulation of their topological transitions pose significant challenges in situ. In this study, we have successfully constructed an array of discrete structures based on a series of bidentate pyridyl ligands (L1, L2, and L3), which were subsequently ligated with half-sandwiched (Cp*Ir fragments) building blocks. Our further investigations elucidate a strategy for coordinating the relative lengths of the bidentate ligands with the building blocks, achieving specific concentrations that drive the transformation of tetranuclear metal macrocycles into Borromean rings. Notably, the distinct characteristics of the three pyridyl ligands markedly influence the efficiency of synthesis and the topological conversion of the supramolecular macrocycles. Detailed structural analyses reveal that π-π stacking interactions, the electron-donating capabilities of the ligands, and hydrogen-bonding interactions are pivotal in stabilizing these molecular macrocycles and in facilitating their transformation to Borromean rings. The analyses underscore the importance of the electron-rich effect induced by the sulfur atoms in the ligands and the regulation and modulation of the pyridine functional group in contributing to the structural stability and altered characteristics of the macrocycles.

On Borromean links and related structures.

The creation of knotted, woven and linked molecular structures is an exciting and growing field in synthetic chemistry. Presented here is a description of an extended family of structures related to the classical `Borromean rings', in which no two rings are directly linked. These structures may serve as templates for the designed synthesis of Borromean polycatenanes. Links of n components in which no two are directly linked are termed `n-Borromean' [Liang & Mislow (1994). J. Math. Chem. 16, 27-35]. In the classic Borromean rings the components are three rings (closed loops). More generally, they may be a finite number of periodic objects such as graphs (nets), or sets of strings related by translations as in periodic chain mail. It has been shown [Chamberland & Herman (2015). Math. Intelligencer, 37, 20-25] that the linking patterns can be described by complete directed graphs (known as tournaments) and those up to 13 vertices that are vertex-transitive are enumerated. In turn, these lead to ring-transitive (isonemal) n-Borromean rings. Optimal piecewise-linear embeddings of such structures are given in their highest-symmetry point groups. In particular, isonemal embeddings with rotoinversion symmetry are described for three, five, six, seven, nine, ten, 11, 13 and 14 rings. Piecewise-linear embeddings are also given of isonemal 1- and 2-periodic polycatenanes (chains and chain mail) in their highest-symmetry setting. Also the linking of n-Borromean sets of interleaved honeycomb nets is described.

Self-assembly of metalla[3]catenanes, Borromean rings and ring-in-ring complexes using a simple π-donor unit.

Despite extensive research and several stunning breakthroughs in the synthesis of interlocked molecular species, [3]catenanes, Borromean rings and ring-in-ring complexes are exceedingly rare and their targeted synthesis remains a formidable challenge. Herein, a series of Cp*Rh-based homogeneous and heterogeneous interlocked structures have been prepared by coordination-driven self-assembly, not only including metalla[2]catenanes and molecular Borromean rings, but also linear metalla[3]catenanes and ring-in-ring complexes. The interlocked structures are all based on bithiophenyl groups. The bithiophenyl groups effectively enhance the strength of the inter-ring interactions and play a crucial role in the formation of these interlocked structures. By taking advantage of the strong interaction between π-donor (D) and π-acceptor (A) groups, the electron-deficient methylviologen cation was introduced into a cationic metallarectangle based on bithiophenyl groups. Taking inspiration from these results, a cationic metallarectangle based on A units was threaded into a metallarectangle based on D units, leading to a heterogeneous D-A ring-in-ring structure.

Selective Synthesis of Discrete Mono-, Interlocked-, and Borromean Ring Ensembles Based on a π-Electron-Deficient Ligand.

Herein, we present a new synthetic approach to achieve selective supramolecular transformations and construct different interlocked metallacycles featuring a π-electron-deficient thiazolo[5,4-d]thiazole-derived ligand. We demonstrate that the formation of mono-rings, interlocked rings ([2]catenanes) and Borromean rings can be controlled by adjusting the length of the binuclear half-sandwich RhIII and IrIII building blocks. Furthermore, a concentration effect or D-A stacking interaction between the pyrene guest and the thiazolo[5,4-d]thiazole-based ligand promotes a unique and reversible conversion between catenane structures and metalla-rectangles. The synthetic results are supported by single-crystal X-ray diffraction analysis.

"A professora de piano" e a questão da perversão / "the piano teacher" and the question of perversion

ABSTRACT: This article aims to demonstrate how perversion, as a subject, activates investigation. As a starting point, it explores Freud's idea surrounding fetishism as a paradigm of itself; a necessary interval between neurosis and psychosis. This analysis is followed by a presentation of various notions developed by Lacan in his teachings. Subsequently, the article analyzes Haneke's 2001 film "The piano teacher", here considered as a case of substitute perversion that adds to the few documented cases of this nature. The movie contributes elements that allow to think about and further develop the notion of substitute perversion in psychosis. In it, "the teacher" demonstrates the separation between love, desire, juissance and what Lacan calls "false hole" through borromean rings. Lastly, questions are posed regarding perversion; organized by answers, opposite the two aforementioned structures.

Resumo: O artigo ocupa-se de mostrar como a perversão é uma temática que ativa a pesquisa. Explora, inicialmente, a ideia de Freud sobre o fetichismo como paradigma desse operador clínico, intervalo necessário entre a neurose e a psicose. Depois apresenta noções formuladas por Lacan em seus ensinamentos. Examina, posteriormente, o filme A professora de piano, de Haneke (2001), considerando-o material que contribui diante da escassez de casos sobre perversão. Encontra no filme elementos para pensar e indagar a suplência perversa na psicose. A professora ensina a propósito da amarração do nó borromeano entre amor, desejo, gozo e do estabelecimento do que Lacan chama: "falso furo". O artigo, finalmente, formula questões sobre essa estrutura clínica que, diferentemente das outras duas, se organiza não em certezas, mas adiantando respostas.