Chloroform-Soluble Schiff-Base Zn(II) or Cd(II) Complexes from a Dynamic Combinatorial Library

Epstein, Daniel M.; Choudhary, Seema; Churchill, Melvyn Rowen; Keil, Kim M.; Eliseev, and Alexey V.; Morrow, Janet R.

doi:10.1021/ic000938t

Cited by 133 publications

(66 citation statements)

References 25 publications

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“…54 Azobenzene moieties are one of the more commonly used groups. 110,[112][113][114] The UV induced change from the trans conformation to the cis conformation often results in disruption of the gel state resulting in a solution. Shinkai was one of first to use this principle although many others have followed this work up with many applications, such as drug delivery, 1 and insightful studies such as the cooperative effects of this transformation within the self-assembled fibres.…”

Section: 1mentioning

confidence: 99%

“…106,107,[109][110][111]122 For this reason CBZ seemed ideal to test against crystallisation within our gels. CBZ, an anticonvulsant, crystallises in four known anhydrous, solventless forms (although the trigonal form could contain some solvent).…”

Section: Cbzmentioning

confidence: 99%

“…As the tridentate chelating deprotonated 3.11a is rigid and planar the coordination of two ligands around a metal centre results in the mer isomer, which has been isolated in this crystallisation. 109,110 As…”

Section: -108mentioning

confidence: 99%

“…[106][107][108][109][110][111] Aspirin was also chosen as a drug compound which shows very little change in its structural crystallography in terms of polymorphism (there are two possible polymorphs) and habit growth. …”

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Anion-tuning of supramolecular gel properties

2009

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Section: 1mentioning

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Section: Cbzmentioning

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Anion-tuning of supramolecular gel properties

2009

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“…The present species 1(M) (Fig. 1) incorporate ligands 2 containing two coordination subunits [of a type described earlier (30)] built from a central pyrimidine bridging unit connected via imine bonds to two lateral phenoxy groups (see Scheme1).…”

Section: Concept: Design Of the Systemmentioning

confidence: 99%

Self-organization by selection: Generation of a metallosupramolecular grid architecture by selection of components in a dynamic library of ligands

Nitschke

Lehn

2003

Proc. Natl. Acad. Sci. U.S.A.

136

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Self-organization by selection is implemented in the generation of a tetranuclear [2 ؋ 2] grid-type metallosupramolecular architecture from its components. It occurs through a two-level self-assembly involving two dynamic processes: reversible covalent bound connection and reversible metal ion coordination. Thus, mixing the aminophenol 3, the dialdehyde 4, and zinc acetate generates the grid complex 1a(Zn) via the assembly of the ligand 2a by imine formation and of the grid by zinc(II) binding. When the same process is conducted in a solution containing a mixture of different aminophenol and carbonyl components, the generation of the grid 1a(Zn) drives the selection of the correct components in a virtual dynamic library of ligands, displaying an amplification factor of >100 and a selectivity of >99%. Component exchange as well as reversible protonic modulation of the assembly͞disassembly process display the dynamic character of the system and its ability to respond͞adapt to changes in environmental conditions. The processes described demonstrate the implementation of a two-level self-organization by selection operating on the dynamic diversity generated by a set of reversibly connected components and driven by the formation of a specific product in a ''self-design'' fashion.S elf-organization (1-7) of chemical entities of higher complexity from their components may be directed by the design of both these components and their mode of assembly, i.e., by the molecular information stored in the components and by the supramolecular processing of this information through the interactional algorithm (the interaction pattern) involved. Its sensitivity to changes in internal or external parameters defines the robustness, or conversely the adaptability, of the organizational program. The implementation of self-organization processes represents a major goal of supramolecular chemistry and rests on the design of adequately programmed chemical systems.The dynamic nature of supramolecular entities furthermore endows the system with selection, adaptation, and evolution features. Thus, in addition to self-organization by design, selforganization by selection may take place, provided a dynamic diversity of constituents is produced in the system on which selection may operate (7). Such diversity generation results when a collection of components undergoes continuous recombination of their connections to yield a set of interconverting constituents. It defines a constitutional dynamic chemistry operating on both the molecular and supramolecular levels (7).The latter involves noncovalent interactions, which are reversible by nature, and is therefore dynamic by essence. It is illustrated, for instance, in the self-selection of ligand strands in helicates (8) and building blocks in supramolecular cages, capsules (9-11), and polymers (12).The former covalent constitutional dynamic chemistry is dynamic by design because it requires the deliberate introduction of reversible covalent bonds to allow for constitutional variation through exc...

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Choudhary

Morrow

2002

Angew. Chem.

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Metal ion coordination chemistry is well suited to dynamic combinatorial chemistry approaches. [1±3] Diverse metal ion complex libraries can be created simply by mixing a labile metal ion with different ligands. [4] If ligand exchange is rapid, these metal ion complexes form the equilibrating components of a dynamic library. The equilibrium between complexes may be shifted upon addition of molecular targets. For example, small molecule or biopolymer targets perturb the equilibrium between metal ion complexes to increase the concentration of the metal ion complex that best binds the target. [5±7] We previously reported on dynamic combinatorial libraries of metal ion Schiff-base complexes of limited diversity. [8] Our selection protocol utilizes extraction of metal ion complex libraries from aqueous into organic solvent. In this method, the organic solvent is the ultimate target and complexes with the greatest stability and solubility in organic solvent versus aqueous solution are selected. [9] Here we present studies using acylhydrazone ligand libraries and show that these libraries lead to improvements in efficiency and selectivity of metal ion extraction in comparison to single ligand systems.Acylhydrazone ligands (Scheme 1) were chosen to explore the possibility of forming a double-orthogonal library [4] by exchange at metal±ligand (MÀL) and C¼N bonds. [10±13] Initial studies were carried out to establish the feasibility of using these exchange processes. Zn II extracts into chloroform from a buffered aqueous solution in the presence of two equivalents of acylhydrazone ligand 1 (Table 1, Scheme 1). The predominant complex that extracts into chloroform is the neutral complex [Zn(1 À ) 2 ] as determined by comparison of 1 H NMR and mass spectral data to that of an authentic sample. After two hours, the extent of extraction of Zn II from a water/chloroform mixture containing 0.0500 mm [Zn(1 À ) 2 ] is identical within experimental error to a second experiment containing 0.0500 mm Zn(NO 3 ) 2 and 0.100 mm 1, confirming that our system is at equilibrium. Addition of a different acylhydrazone ligand (13) to either of the solutions above followed by stirring for 2 h increases the amount ZUSCHRIFTEN 4270

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Chloroform-Soluble Schiff-Base Zn(II) or Cd(II) Complexes from a Dynamic Combinatorial Library

Cited by 133 publications

References 25 publications

Anion-tuning of supramolecular gel properties

Anion-tuning of supramolecular gel properties

Self-organization by selection: Generation of a metallosupramolecular grid architecture by selection of components in a dynamic library of ligands

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