Log K, Delta H, and Delta S values for interactions of a series of pyridinoazacrown ethers each bearing a phenol arm (2-6) and two macrocycles each bearing a pyridine arm (7, 8) with Na+, K+, Tl+, and Ag+ have been determined in absolute methanol at 25 degrees C by calorimetric titration. In each case, the complex stability has the sequence Naf < K+ < Tl+ much less than Ag+. The phenol-armed macrocycles exhibit selectivity of more than 4 orders of magnitude for Ag+ over Na+, K+, and Tl+. Attachment of a pendant phenol arm having various substituents to parent macrocycle 1 increases the binding abilities of the resulting ligands. Substituents on the para position of the phenol arm have an appreciable effect on cation-binding constants. Good Hammett correlations are found by plotting log K values vs sigma(p) for interactions of five phenol-armed macrocyclic ligands (2-6) with Na+, K+, and Tl+. The complexation has been characterized by means of H-1 NMR and UV-visible spectroscopic, and X-ray crystallographic methods. The crystal data for Na+-3: formula, [Na(C23H28.5N3O5)](ClO4)(0.5); space group, P (1) over bar; a = 9.400(9) Angstrom, b = 11.467(10) Angstrom, c = 12.281(11) Angstrom, alpha = 77.22(7)degrees, beta = 87.73(7)degrees, gamma = 86.39(7)degrees, V = 1288(2) Angstrom(3), and Z = 2. The study indicates that the phenol OH group of 2-6 is capable of forming an intramolecular hydrogen bond with the macroring nitrogen atom and that the complexation in absolute methanol generally does not deprotonate these phenols. In the crystal structure of the Na+-3 complex, the Na+ is coordinated to all seven of the donor atoms of the ligand and two Na+-3 complexes join together to form a dimer. The dimer contains an intermolecular hydrogen bond formed between the phenol hydrogen atom of one ligand and the phenolate group of a centrosymmetrically related ligand and two pi-pi stacking interactions between the electron-deficient pyridine ring of one molecule and the electron-rich phenol ring of the other.

Methods for the synthesis of pyridinocrowns functionalized with various proton ionizable groups have been elaborated. Sixteen new ligands containing pyridine rings as part of the macrocycle or as a side arm have been prepared. Different interactive abilities of the OH and NH functions of 3,9-dioxa-6-azaundecane-1,11-diol (3) in strong base allowed the synthesis of pyridinoazacrowns 1 and 2 by cyclization with 2,6-bis((tosyloxy)methyl)pyridine (4) and THP-protected 4-hydroxy-2,6-bis(tosyloxy)methyl)pyridine (5). Pyridinoazacrown 1 was functionalized with different proton ionizable side arms by treatment first with formaldehyde in methanol to form the N-methoxymethyl derivative 6 and then treating 6 with 5-chloro-8-hydroxyquinoline or the appropriate substituted phenol. Pyridinoaza-18-crown-6 ligands containing p-methylphenol (7), p-methoxyphenol (8), p-chlorophenol (9),p-fluorophenol (10),p-cyanophenol (11), 2-formyl-4-bromophenol (12), or 5-chloro-8-hydroxyquinoline (13) groups were prepared by this process. Pyridinoazacrowns 1 and 2 were alkylated with 2-hydroxy-5-nitrobenzyl chloride or 5-chloro-8-methoxy-2-(bromomethyl)quinol followed by removal of the protecting groups to form p-nitrophenol- and 5-chloro-8-hydroxy-2-quinolinyl-substituted ligands (16, 18, and 21). Macrocycles 22 and 23 containing proton ionizable triazole and phenol functions inside the macrocyclic cavity and a pyridine side arm were prepared by cyclization of the appropriate dihalide with 6-(2'-pyridylmethyl)-3,9-dioxa-6-azaundecane-1,11-diol followed by cleavage of the THP or methoxy protecting groups. Preliminary complexation data show that the phenol-substituted pyridinoaza-18-crown-6 ligands form strong complexes with various metal cations and exhibit high selectivity toward Ag+. Macrocycle 16 containing a p-nitrophenol substituent formed a complex with benzylamine. The crystal structures for 16 and its benzylamine complex are also given here.

An achiral (3) and two chiral pyridine-based macrobicyclic clefts (4 and 5) have been prepared by treating 2,6-bis[[2',6'-bis(bromomethyl)-4'-methylphenoxy]pyridine (2) with the appropriate achiral and chiral glycols. Starting 2 was prepared by first treating 2,6-bis(hydroxymethyl)-4-methylphenol with 2,6-[(tosyloxy)methyl]pyridine followed by phosphorus tribromide. Achiral macrobicyclic cleft 3 formed a complex at 25 degrees C in 50% CH3OH/50% CHCl3 (v/v) with a primary ammonium salt (log K=3.15) as evidenced by a significant change in the (1)HNMR spectrum. Highly organized (S,S,S,S)4, prepared by treating 2 with (1S,5S)-3-oxapentane-1,5-diol, exhibited recognition at 25 degrees C in 20% C2H5OH/80% 1,2-C2H4Cl2 (v/v) for the (S)-enantiomer of alpha-(1-naphthyl)-ethylammonium perchlorate (NapEt) over its (R)-form (Delta log K=0.85). This high recognition factor probably reflects an increase in molecular rigidity by the introduction of a second macro ring on the monocyclic pyridinocrown ligand.

: An achiral (3) and two chiral pyridine-based macrobicyclic clefts (4 and 5) have been prepared by treating 2,6-bis(2',6'-bis(bromomethyl)-4'- methylphenoxymethyl)pyridine (2) with the appropriate achiral and chiral glycols. Starting 2 was prepared by first treating 2,6- bis(hydroxymethyl)-4-methylphenol with 2,6-pyridinedimethyl ditosylate followed by phosphorus tribromide.

Functionalisation of a mononuclear barium complex of a 24-membered bibracchial tetraimine Schiff-base macrocycle (L(1)) derived from the barium-templated cyclocondensation of 2,6-diacetylpyridine and tris(2-aminoethyl)amine was attempted using salicylaldehyde. The reaction leads to the isolation of the tripodal ligand tris[2-(salicylideneamino)ethyl] amine (L(2)) and the complex BaL(2)(2)(ClO4)(2). The crystal structures of the parent macrocyclic complex, [BaL(1)] [ClO4](2) [monoclinic, space group P2(1)/c (no. 14). a = 11.755(7), b = 21.733(17), c = 15.621(15) Angstrom, beta = 90.50(7)degrees, Z = 4], and BaL(2)(2)(ClO4)(2) [monoclinic, space group P2(1)/c (C-2/1(5), no. 14), a =12.299(15), b = 9.530(15). c = 25.798(32) Angstrom, beta = 108.679(9)degrees, Z = 2] have been determined.

The synthesis and X-ray crystal structure of a disilver complex [Ag2L1] [BF4]2 of a bibracchial tetraimine Schiff-base macrocycle derived from the silver-templated cyclocondensation of 2,6-diacetylpyridine and tris(2-aminoethyl)amine are reported. The complex crystallises in the monoclinic space group P2(1)/n (a non-standard setting of P2(1)/c, no. 14) and has unit-cell dimensions a = 11.660(22), b = 28.14(4), c = 12.1 58(21) angstrom, beta = 107.94(13)-degrees with Z = 4. Functionalisation of the pendant arms with salicylaldehyde followed by transmetallation with Cu(II) leads to the formation of a trinuclear copper(II) complex [Cu3L4-(OH)][ClO4]3.2H2O in which there is a single Cu(II) atom 4.9 and 5.9 angstrom distant from a pair of Cu(II) atoms which are 3.6 angstrom apart and hydroxy-bridged. The complex, which crystallises in the monoclinic space group P2,(no. 4) and has unit cell dimensions a = 13.997(24), b = 16.043(9), c = 14.353(11) angstrom, beta = 118.97(10)-degrees with Z = 2, may be regarded as a first-generation model for ascorbate oxidase. A study of the magnetic properties shows that the trinuclear copper(II) complex can be regarded as a mononuclear site non-interacting with a moderately coupled copper pair (2J = -202 cm-1).

The challenge presented by the design and synthesis of ligands capable of organising more than two metal centres into a predetermined arrangement in order to develop new materials is discussed.The design and synthesis of macropolycyclic and/or macropolyacyclic Schiff bases, which have the potential to act as metal-specific ligands, or can allow the simultaneous incorporation of two or more metals in well defined homo- or heterodinuclear arrays, is presented together with the role of metal ions as templating devices and the opportunities to utilise transmetallation reactions. Formation of Schiff bases followed by reductive demetallation leads to a variety of more stable, and flexible, ligands useful in metal transfer studies. C- and N-functionalisation of macrocyclic Schiff bases produces pendant-armed ligands which permit a more dynamic complexation of the metal ion than is found in bicyclic ligands.

The synthesis and characterisation of acyclic mononuclear and macrocyclic dinuclear silver(I) complexes of ligands derived from the Schiff base condensation of N,N-bis(2-aminoalkyl)-2-phenylethylamines with 2,6-diacetylpyridine are reported and discussed. It is noted that changing the 2-aminoalkyl groups of the alkylamines from ethyl to n-propyl provides a change from an acyclic mononuclear silver(I) compound to a macrocyclic dinuclear silver(I) compound.

The X-ray structure of a mononuclear barium complex of the bibracchial tetraimine Schiff-base macrocycle derived from the cyclocondensation of 2,6-diacetylpyridine and NN-bis(2-aminoethyl)-2-methoxyethylamine [monoclinic, space group P2/n (no. 13), a = 27.494(20), b = 14.120(13), c = 21.024(14) angstrom, beta = 91.68(57)-degrees, Z = 8] confirms that the macrocycle folds to present a molecular cleft within which the metal is co-ordinated. Transmetallation with Cu(II) gives a homodinuclear copper(II) complex the crystal structure of which [monoclinic, space group P2(1)/c, a = 14.807(6), b = 9.558(4), c = 17.432(8) angstrom, beta = 113.89(5)-degrees, Z = 2] shows that the copper(II) atoms are held by the 'head' units of the macrocycle, an opening of the cleft having occurred.

A disilver(I) complex of a tetraimine Schiff-base macrocycle with stabilised N-isopropylidene-bearing pendant arms has been synthesised and its crystal structure shows that the molecule does not possess the cleft-like appearance previously noted for related disilver(I) complexes.

The synthesis and X-ray crystal structure of a triangulo-copper(II) complex which may be regarded as a first generation model for the triangular copper(II) site in ascorbate oxidase is described.