New proton-ionizable macrocyclic ligands. Synthesis, basicity, reactions, and structures of two aza crown ethers containing the 4-hydroxypyridine unit

Abstract

Two new reactive aza crown ethers, (1) and (2), containing the 4-hydroxypyridine unit have been prepared and found to be different with respect to pK(HpO) values for H2L+, structures of the hydrates of HL, and complex formation with benzylamine and the benzylammonium ion.Crown ethers containing reactive groups are important as intermediates for the preparation of functionalized crown derivatives such as lariat ethers, bis(crown ethers), synthetic ionophores, immobilized crown ethers, and crown polymers. 1 Interest in these applications has resulted in the development of a variety of synthetic procedures for the preparation of hydroxymethyl crown ethers, which are representative of such compounds.2 We report here the synthesis of two new macrocycles (1) and (2). Each of these compounds contains the 4-hydroxypyridine unit, but their reactions, basicity, and structures are distinctly different.

Ion Extraction and Transport by Proton-Ionizable Crown Ethers

“…(1) attachment of a pendant side arm which includes or is terminated by an ionizable entity [7,12,; (2) inclusion within the crown ether framework of a subunit which projects an ionizable entity, so that both the proton and the atom which bears it are within the cavity [67][68][69][70][71][72][73][74][75]; and (3) inclusion, as part of the crown ether framewotk, of a unit which places a heteroatom in a ligating position, with an attached proton projecting into the ring cavity [76][77][78][79][80][81][82][83][84].…”

“…To date all attempts to do this have made use of nitrogen atoms in hydroxypyridine or pyridone (CCIV-CCXX) [76,78,80,82,84], triazole (CCXXI-CCXXXII) [77,81], or sulfonamide (CCXXXIII-CCXLII) [79,83] Cmpd CCXLll Cmpd Ref CCXXXVIII [83] CCXXXIX [83] CCXL [83] CCXLI [83] Ref [83] 3. Complexation Behavior of Proton-Ionizable Macrocycles.…”

“…The methods of placing the nitrogen atom in the ring framework include the incorporation of hydroxypyridine or pyridone rings (CCIV-CCXX) [76,78,80,82, 84J, triazo1e subunits (CCXXI-CCXXXII) [77, 81J or sulfonamide groups (CCXXXill-CCXLll) [79, 83J as part of the macrocycic framework.…”

Synthesis of proton-ionizable acyclic, macrocyclic and macrobicyclic compounds containing one or two triazole groups

“…Also, Bradshaw and coworkers have reported a series of diaza-18-crown-6 compounds with pendant phenol and hydroxyquinoline units [7]. Macrocycles with 4-hydroxypyridine [8][9][10][11][12][13] and triazole [13][14][15][16][17] heterocyclic subunits within the macroring have been developed by Brandshaw, Izatt and their coworkers, de Mendoza and Torres and their coworkers [18][19][20][21][22][23][24][25] and others [26][27][28]. Podands [23][24][25][26][27][28][29] and polyaza macrobicyclic cryptands [24] with triazole subunits have been prepared, as well.…”

3-D Hydrogen-Bonded Frameworks of Two Metal Complexes with Chelidamic Acid: Syntheses, Structures and Magnetism

“…[1][2][3][4][5][6][7] In addition, as an emblematical polydentate ligand, it was also of great interest in the study of coordination chemistry. Though the initial report of H 3 Chel was published in 1926, 8 the crystal structure of the H 3 Chel was not determined until 2000. 9 In contrast, the studies concerning the transition metal complexes with chelidamic acid are rare, to our best knowledge, the only known examples consisting of Cr, Fe, Sn, Gd, V and Zn up to now.…”