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Modern chemists know that alchemists were their historical predecessors, yet they are not proud of this relationship, which chemists today tend to hide or forget. However, no discontinuity exists between alchemy and chemistry and we still use laboratory techniques that were invented by alchemists hundreds or thousands of years ago. Alchemists used a secret language and made an extended use of symbols to indicate substances and procedures. When--in the second half of the 18th century--alchemy became quantitative and evolved into the discipline of chemistry, symbols were abandoned and replaced by abbreviations and formulas. However, the nature of the communication about matter by chemists remains mysterious to the uninitiated. (Contains 18 figures and 5 notes.)

The two coordinatively unsaturated complexes [[Cu(cyclam)].sup.2+] (cyclam: 1,4,8,11-tetraazacyclotetradecane, 1) and [[Cu([Bn.sub.4]cyclam)].sup.2+] (Bn4cyclam: 1,4,8,11-tetrabenzyl-1,4,8,11- tetraazacyclotetradecane, 2) in an MeCN solution uptake an anion [X.sup.-] (halide, pseudohalide) to give square pyramidal ternary complexes, whose stability has been determined through spectrophotometric titration experiments. The formation of a five-cordinate complex is favored by the trans-1 configuration of the [[Cu([Bn.sub.4]cyclam)].sup.2+] receptor, but it is contrasted by the severe steric repulsions exerted by the benzyl substituents on the macrocyclic framework. No significant repulsive effects have been observed in anion binding to the [[Cu(cyclam)].sup.2+] receptor, exhibiting a trans-111 configuration. The existence of a linear relationship between the magnitude of the red shift experienced by the d-d absorption band on anion binding and log K values is discussed. Key words: tetraamine macrocycles, anion recognition, five-coordinate complexes, spectroscopic properties/thermodynamic quantities linear relationships. Les complexes coordinativement insatures [[Cu(cyclam)].sup.2+] (cyclam : 1,4,8,11-tetraazacyclotetradecane, 1) et [[Cu([Bn.sub.4]cyclam)].sup.2+] (Bn4cyclam : 1,4,8,11-tetrabenzyl-1,4,8,11-tetraazacyclotetradecane, 2) dans une solution de MeCN solution se fixent a un anion X(halogenure, pseudo-halogenure) pour former des complexes ternaires pyramidaux a base carree dont la stabilite a ete determinee a l'aide d'experiences de titrage spectrophotometriques. La formation d'un complexe pentacoordonne est favorisee par la conformation trans-1 du recepteur [[Cu([[Bn.sub.4]cyclam)].sup.2+] mais elle est genee par les fortes repulsions steriques exercees par les substituants benzyles sur la structure macrocyclique. Aucun effet repulsif significatif n'a ete observe au niveau de la liaison de l'anion au recepteur [[Cu(cyclam)].sup.2+], qui presentait une conformation trans-111. L'existence d'une relation lineaire entre la magnitude du decalage vers le rouge que subit la bande d'absorption d-d au niveau de la liaison anionique et les valeurs de log K est analysee. [Traduit par la Redaction] Mots-cles : tetraamines macrocycliques, reconnaissance anionique, complexes pentacoordonnes, relations lineaires entre proprietes spectroscopiques et quantites thermodynamiques., Introduction Classical coordination chemistry, that involving metal ions, originated from the studies of Alfred Werner on the ammonia complexes with substitutionally inert metal ions ([Co.sup.III], [Cr.sup.III], [Pt.sup.IV]) and dates back [...]

This review tells the story of scorpiands, polyamine ligands which, when specifically stimulated, act as scorpions, and of their metal complexes, scorpiates. Scorpiands consist of a tetramine macrocycle (typically cyclam) capable of firmly including a transition metal and of a side chain ending with a nitrogen containing coordinating group: under unperturbed conditions the coordinating group is bound to the metal (ON), but on addition of acid the nitrogen is protonated and comes off the metal (OFF). Alternating acid/base addition makes the side chain move imitating the tail of a scorpion that bites a prey firmly immobilized by the claws. Occurrence of the ON‐OFF motion is monitored by the colour change of the scorpiate complexes associated to the change of coordination or by fluorescence quenching/restoring when a light‐emitting substituent is linked to the side arm. Scorpiate complexes can be considered optical molecular switches and, from a different standpoint, molecular machines able to convert chemical energy into mechanical work. [ABSTRACT FROM AUTHOR]

Research has been conducted on water soluble Ni (super)II complexes of cyclam derivatives. Results demonstrate that the combination of these complexes with 1,3-benzodioxole and 1,2,3-trimethoxybenzene shows fluorescence emission resulting from the charge transfer excited state.

Research has been conducted on the tetradentante, ditopic, bisimo bisheterocyclic ligands and their complexes with Cu (super)I and Cu (super)II. The study of these ligands and complexes in CH (sub)3 CN solution via (super)1 NMR, mass and UV/vis spectroscopy has been carried out and the results are presented.

The bistern cage L rapidly and reversibly incorporates Ni(super II), Cu(super II) and Zn(super II) ions in aqueous solution to afford a 1:1 stoichiometry. Stable metal complexes of protonated forms of the ligand are present as major species in a slightly acidic solution. The crystal structure of (Ni(super II)(LH+))(ClO4)3 complex reveals that the metal is six-coordinate and displaced toward one end og the cavity, while the proton is bound to one of the secondary N atoms at the other end.

The [NiII(3-benzyl-2,4-dimethyl-1,5,8,12-tetraazacyclotetradecane)]2+ was synthesized by the one-step reaction of dienato NiII complex with diene derivatives followed by the reduction of the imine bonds. The bypiridine- and benzyl-substituted NiII complexes exhibited electrostatic repulsive effects that are generated by the square planar-coordinated, low-spin Ni2+ cation on the protons. Furthermore, the NiII complex interacts with CuII to form a multicomponent coordination compound with a trigonal bipyramidal geometry.

The role of 3d metal ions as templates for electron donor-acceptor systems using an aliphatic polyamine as a spacer has been investigated. The results showed that the Zn(II) coordination by the tetraamine spacer of a two-component system enables the photoinduced electron-transfer to occur by bringing closer the donor dimethyaniline fragment and the fluorophore anthracene subunit.

A scheme for the one-pot synthesis of tetraaza macrocycles using benzaldehyde as the building block has been proposed. The scheme involves the Schiff base condensation of the metal-fee open-chain tetramine with benzaldehyde, formation of the Cu(II) complex and nucleophilic attack by the deprotonated nitroethane fragment to form the macrocyclic fragment. The Schiff base CuII complex and the CuII macrocyclic complex have been isolated in the crystalline form and their molecular structures were determined.

The ligand N,N'-bis(2-aminoethyl)-2-2-(4-pyridyl)ethyl malondiamide, (1b) is a building block of several supramolecular coordination compounds. The coordination of 1b and Cu(II) ion with the diamino-diamido binding unit and release of the two amido protons yields a described complex. The association of two units via their pyridine nitrogen atoms generate the supramolecular species 3 (described) which have weak interactions among the components. The complex 3 possesses exchangeable peripheral transition metal cations.

A template reaction with the open-chain tetramine complex, (NiII(2.3.2-tet))2+, formaldehyde and a locking fragment facilitates synthesis of various functionalized azacyclam complexes of Ni(II). The low-spin (3-(4-tolylsulfonyl)-1,3,5,8, 12-pentaazacyclotetradecane)nickel(II) complex has been analyzed. Three crystallographically-independent cationic complexes are evident in the crystal structure.

Continuous-flow and stopped-flow spectroscopic analyses of the violet colored reaction intermediate in the nickel(II)-catalyzed deprotonation of amine group of cyclam reveals that the intermediate violet color occurs from a strong band at 539 nanometers. The band relates to one of the deprotonated cyclam's ni(III) amine complex. Spectral evaluations specify to an accuracy of 0.1 that Ni-catalyzed deprotonation has a pKa value of about 7.1.

The addition of formaldehyde and pyridine-3-carboxamide or pyridine-4-carboxamide to a (MII 2,3,2-tet)2+ complex resulted in a condensation process that facilitated the bonding of pyridines to metallocyclamsegments. Electrochemical and structural examinations were conducted to characterize the resulting complexes. The metallocyclam-pyridine complexes weresubjected to further reactions involving other metal complexes and redox systems.

The cis-Py2PtII core in the cis-(PtII 3-FcPy 2 Cl2) complex hinders the occurrence of electronic interaction between bis(ferrocenes). The PtII unit efficiently functions as a bridging segment of the two ferrocene structures. Similarly, the (Py2Re CO 3 Cl) core in the (4-FcPy 2 Re CO 3 Cl) complex stops the transfer of electron communication between the structures. The results reveal that the pyridine ring connecting the PtII or Re to the ferrocene substituent is responsible for the stopping property of the core.

Research has been conducted on the reinforced tetramine macrocycle. Results indicate that in the Ni (super)II complex of this macrocycle the fluorophore light emission is pH-controlled.