Biological molecules interact with substrates with exquisite precision and (stereo)chemical selectivity, because of their ability to generate suitable receptor sites for substrate molecules. These sites have sufficient diversity in their bonding capabilities to allow subtle differentiation between molecular geometries. There is, thus, considerable interest in the preparation of synthetic materials with aspects of this function.[1] One approach is to use biologically derived components in the assembly of such materials. Amino acid residues are the origin for the functional properties and highly selective substrate-binding ability of many extended biological structures, and so are an attractive option as chiral building blocks for the preparation of bio-analogous materials. Herein, we report a family of synthetic crystalline nanoporous materials in which the internal surface is provided by the amino acid aspartic acid. These materials display enantioselective sorption that is strongly dependent on the spatial distribution of functional groups within the guest molecule.Aspartic acid (NH 2 CH(COOH)CH 2 COOH, aspH 2 ) is an acidic amino acid with one amine and two carboxylic acid groups. As each of these functional groups is capable of binding to metal centers, the aspartate anion has a variety of coordination modes.[2] This polyfunctionality makes it a suitable organic node for the construction of porous metalorganic open-framework materials. [3][4][5][6] Extended frameworks based on metal aspartates have recently been reported; [2] however, the structural motifs in these frameworks are too dense to generate guest-accessible volume. The lactate [7] and tartrate [8] anions have also been used in the construction of metal-organic frameworks.We have sought to generate porosity by connecting metalaspartate units with suitable bidentate linker molecules. This objective requires a synthetic route that avoids the presence

The design of biomimetic complexes for the modeling of metallo-enzyme active sites is a fruitful strategy for obtaining fundamental information and a better understanding of the molecular mechanisms at work in Nature's chemistry. The classical strategy for modeling metallo-sites relies on the synthesis of metal complexes with polydentate ligands that mimic the coordination environment encountered in the natural systems. However, it is well recognized that metal ion embedment in the proteic cavity has key roles not only in the recognition events but also in generating transient species and directing their reactivity. Hence, this review focuses on an important aspect common to enzymes, which is the presence of a pocket surrounding the metal ion reactive sites. Through selected examples, the following points are stressed: (i) the design of biomimetic cavity-based complexes, (ii) their corresponding host-guest chemistry, with a special focus on problems related to orientation and exchange mechanisms of the ligand within the host, (iii) cavity effects on the metal ion binding properties, including 1st, 2nd, and 3rd coordination spheres and hydrophobic effects and finally (iv) the impact these factors have on the reactivity of embedded metal ions. Important perspectives lie in the use of this knowledge for the development of selective and sensitive probes, new reactions, and green and efficient catalysts with bio-inspired systems.

We report the synthesis, characterization, and solution chemistry of a series of new Fe(II) complexes based on the tetradentate ligand N-methyl-N,N'-bis(2-pyridyl-methyl)-1,2-diaminoethane or the pentadentate ones N,N',N'-tris(2-pyridyl-methyl)-1,2-diaminoethane and N,N',N'-tris(2-pyridyl-methyl)-1,3-diaminopropane, modified by propynyl or methoxyphenyltriazolyl groups on the amino functions. Six of these complexes are characterized by X-ray crystallography. In particular, two of them exhibit an hexadentate coordination environment around Fe(II) with two amino, three pyridyl, and one triazolyl groups. UV-visible and cyclic voltammetry experiments of acetonitrile solutions of the complexes allow to deduce accurately the structure of all Fe(II) species in equilibrium. The stability of the complexes could be ranked as follows: [L(5)Fe(II)-py](2+) > [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)-triazolyl](2+) > [L(5)Fe(II)-(NCMe)](2+), where L(5) designates a pentadentate coordination sphere composed of the two amines of ethanediamine and three pyridines. For complexes based on propanediamine, the hierarchy determined is [L(5)Fe(II)-Cl](+) > [L(5)Fe(II)(OTf)](+) > [L(5)Fe(II)-(NCMe)](2+), and no ligand exchange could be evidenced for [L(5)Fe(II)-triazolyl](2+). Reactivity of the [L(5)Fe(II)-triazolyl](2+) complexes with hydrogen peroxide and PhIO is similar to the one of the parent complexes that lack this peculiar group, that is, generation of Fe(III)(OOH) and Fe(IV)(O), respectively. Accordingly, the ability of these complexes at catalyzing the oxidation of small organic molecules by these oxidants follows the tendencies of their previously reported counterparts. Noteworthy is the remarkable cyclooctene epoxidation activity by these complexes in the presence of PhIO.