Structural constraints for the formation of macrocyclic rhombimines

Rhombimines, macrocyclic tetraimines, have been obtained by the condensation of enantiomerically pure trans-1,2-diaminocyclohexane with aromatic dialdehydes connected by a one-atom bridge. The efficiency of the cyclocondensation is dependent upon the nature of the dialdehyde bridge atom: low selectivity was observed and rationalized by computational analysis for sp2 hybridized bridge atoms. Unusual triple-split exciton Cotton effects were measured and calculated for highly symmetrical, tetrachromophoric rhombimines.

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Rhombimine SC40H40N4S2Δε (λ, nm) = −26 (315); +32 (275); −22 (257), in MeCNChirality source: enantiomerically pure (1R,2R)-1,2-diaminocyclohexane

Rhombimine CC42H44N4Δε (λ, nm) = −36 (275); +152 (257); −30 (239), in MeCNChirality source: enantiomerically pure (1R,2R)-1,2-diaminocyclohexane

Rhombimine SiC44H52N4Si2Δε (λ, nm) = −37 (270); +20 (247), in MeCNChirality source: enantiomerically pure (1R,2R)-1,2-diaminocyclohexane

Rhombimine NC52H50N6Δε (λ, nm) = −16 (375); +9 (349); −5 (327), in MeCN-dioxaneChirality source: enantiomerically pure (1R,2R)-1,2-diaminocyclohexane