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Molecular Architecture. 2. Synthesis and Metal Complexation of Heptacyclic Terpyridyl Molecular Clefts
journal contribution
posted on 1998-03-13, 00:00 authored by Thomas W. Bell, Peter J. Cragg, Albert Firestone, Albert D.-I. Kwok, Jia Liu, Richard Ludwig, Andrej SodomaMethods are described for the synthesis of a series of
functionalized derivatives of 9-butyl-1,2,3,4,5,6,7,8-octahydroacridine (9), a building block for
several types of highly preorganized host
compounds. A key intermediate is
5-benzylidene-9-butyl-2,3,5,6,7,8-hexahydroacridin-4(1H)-one
(23), which can also be used in the syntheses of torands and
hydrogen-bonding hexagonal lattice
receptors. A tridentate cleft (20), consisting of
2,2‘;6‘,2‘‘-terpyridine imbedded in a heptacyclic
framework, and a corresponding pentadentate diketone (6)
were synthesized from 9 in five and
seven steps, respectively. The picrate extraction method was used
to estimate the solution stabilities
of alkali metal complexes of heptacyclic terpyridyls 6 and
20, which was also compared with a
flexible terpyridyl (37). Alkali metal complexes of
both heptacyclic terpyridyls showed relatively
high Ks values, but low size selectivity.
Pentadentate host 6 binds Na+ and
K+ more strongly than
do most hexadentate crown ethers; flexible tridentate analogue
37 failed to extract alkali metal
picrates into chloroform. The complexation abilities of
6 and 20 are attributed to enforced
orientation of functional group dipoles toward the center of the
molecular cleft. Sodium and
potassium picrate complexes of pentadentate cleft 6 were
synthesized (1:1 stoichiometry), and a
2:1 complex of calcium triflate
(62·Ca(CF3SO3)2)
was also prepared.
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Keywords
heptacyclic frameworkAlkali metal complexes2. Synthesisfunctionalized derivativesheptacyclic terpyridylsalkali metal complexesPentadentate host 6Metal Complexationhexadentate crown etherspreorganized host compoundsgroup dipolesheptacyclic terpyridyls 6pentadentate diketonealkali metal picratesbuilding blockcomplexation abilitiesMolecular Architecturesolution stabilitiessize selectivitytridentate analogue 37Heptacyclic Terpyridyl Molecular Clefts Methodslattice receptorspicrate extraction methodtridentate cleftpentadentate cleft 6potassium picrate complexescalcium triflate
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