Self-Sorting of Two Imine-Based Metal Complexes: Balancing Kinetics and Thermodynamics in Constitutional Dynamic Networks

A major hurdle in the development of complex constitutional dynamic networks (CDNs) is the lack of strategies to simultaneously control the output of two (or more) interconnected dynamic processes over several species, namely reversible covalent imine bonds formation and dynamic metal-ligand coordination. We have studied in detail the factors influencing the fidelity of the self-sorting process (concentration, electronic and steric parameters of the organic components, nature of the metal cations) of 11 constitutional dynamic libraries containing two different amines, aldehydes and metals salts into two imine-based metal complexes, having no overlap in term of their compositions. In all the cases, the outcome of the process was primarily determined by the ability of the octahedral metal ions to select its pair of components from the initial pool of components, the composition of the weaker tetrahedral complex being imposed by the components rejected by the octahedral metal ions. Different octahedral metal ions required different level of precision in the “assembling instructions” provided by the organic components of the CDN to guide it towards a sorted output. The concentration of the reaction mixture, the electronic and steric properties of the initial components of the library were all found to influence the lifetime of unwanted metastable intermediates formed during the assembling of the two complexes.

Self-Sorting of Two Imine-Based Metal Complexes: Balancing Kinetics and Thermodynamics in Constitutional Dynamic Networks

A major hurdle in the development of complex constitutional dynamic networks (CDNs) is the lack of strategies to simultaneously control the output of two (or more) interconnected dynamic processes over several species, namely reversible covalent imine bonds formation and dynamic metal-ligand coordination. We have studied in detail the factors influencing the fidelity of the self-sorting process (concentration, electronic and steric parameters of the organic components, nature of the metal cations) of 11 constitutional dynamic libraries containing two different amines, aldehydes and metals salts into two imine-based metal complexes, having no overlap in term of their compositions. In all the cases, the outcome of the process was primarily determined by the ability of the octahedral metal ions to select its pair of components from the initial pool of components, the composition of the weaker tetrahedral complex being imposed by the components rejected by the octahedral metal ions. Different octahedral metal ions required different level of precision in the “assembling instructions” provided by the organic components of the CDN to guide it towards a sorted output. The concentration of the reaction mixture, the electronic and steric properties of the initial components of the library were all found to influence the lifetime of unwanted metastable intermediates formed during the assembling of the two complexes.

Crystallization-induced amide bond formation creates a boron-centered spirocyclic system

The 5-nitrosalicylate ester of 2-acetamidophenylboronic acid (C15H10BN2O6) is formed under crystallization conditions from the 5-nitrosalicylate ester of 2-aminophenylboronic acid. The boron at the center of this structure exists as a tetrahedral complex produced by a dative bond with the amide carbonyl. The perpendicular shape produces an unusual packing structure including a bifurcated hydrogen bond between the amide hydrogen and carbonyl groups on two neighboring molecules. We propose that this reaction occurs due to increased Lewis acidity of the nitrosalicylate ester of 2-aminophenylboronic acid.

Validation and correction of Zn–Cys x His y complexes

Many crystal structures in the Protein Data Bank contain zinc ions in a geometrically distorted tetrahedral complex with four Cys and/or His ligands. A method is presented to automatically validate and correct these zinc complexes. Analysis of the corrected zinc complexes shows that the average Zn–Cys distances and Cys–Zn–Cys angles are a function of the number of cysteines and histidines involved. The observed trends can be used to develop more context-sensitive targets for model validation and refinement.

Coordination variability of Copper(I) in multidonor heterocyclic thioamides.

The chemistry of copper(I) with scarcely studied heterocyclic thioamides, namely, 2,4,6-trimercaptotriazine, purine-6-thione, 2,4-dithiouracil, 2-thiouracil and pyrimidine-2-thione is described. The interaction of 2,4,6-trimercaptotriazine (tmtH3) with [Cu(CH3COO)(PPh3)2] gave rise to a pair of bond isomers : [Cu(κ1N-tmtH2)(PPh3)2] (6a), [Cu(κ1N,κ1S-tmtH2)(PPh3)2] (6b) and with copper(I) bromide and PPh3, it has formed a trinuclear complex, [Cu3Br2(κ1N,κ1S,κ2S-tmtH2)(PPh3)6] (7) with anionic tmtH2- in these complexes. The 2,4-dithiouracil with copper halides (CuCl, CuBr) and PPh3 yielded dinuclear complexes: [Cu2(κ2Cl)(κ1S,κ1S-dtucH)(PPh3)4] (4) and [Cu2(κ2Br)(κ1S,κ1S-dtucH)(PPh3)4] (5) with unusual eight membered metallacyclic rings. Pyrimidine-2-thione (pymSH) coordinated to CuI as N,S-chelated anion yielding mononuclear complex, [Cu(κ1N,κ1S-pymS)(PPh3)2] (1), while 2-thiouracil (tucH2) with copper(I) chloride and PPh3 yielded a tetrahedral complex, [CuCl(κ1S-tucH2)(PPh3)2] (3). Purine-6-thione (purSH2) coordinated to CuI in two different modes yielding mono- and di-nuclear complexes, [Cu(κ1N,κ1S-purS)(PPh3)2].CH3OH (2a) and [Cu2(κ1N,κ2S-purS)2(PPh3)2] (2b). The existence of bond isomers (6a and 6b), synthesis of novel dinuclear ( 4 and 5) and rare trinuclear (7) complexes with unusual bonding patterns and uncommon chelation to CuI by pymS- in 1 are the novel features of the present study. Complexes have shown intense emission bands in the visible region, λmax 490 to 495 nm.

Magnetoacoustic Investigation of the Jahn-Teller Effect in Chromium Doped ZnSe Crystal

Ultrasonic investigation of ZnSe:Cr2+crystal was carried out at low temperatures in magnetic field applied along the wave vector. The observed anomalies in magnetic field dependences of attenuation and wave number evidence for existence of resonant transitions between the energy levels of the Jahn-Teller tetrahedral complex CrSe4.