Supramolecular Dimers of Copper(II) Complexes Resulting from Designed Host–Guest Interactions

Abstract

Abstract Syntheses, characterization and crystal structures of fourdesigned host–guest compounds of the compositions [{Cu II L 1 } 2 ⊂(H 3 N(ethylene)NH 3 )](NO 3 ) 2 ( 1 ), [{Cu II L 1 } 2 ⊂(H 3 N(propylene)NH 3 )](NO 3 ) 2 ( 2 ), [{Cu II L 1 } 2 ⊂(H 3 N(butylene)NH 3 )](NO 3 ) 2 ( 3 ) and [{Cu II L 2 } 2 ⊂(H 3 N(ethylene)NH 3 )](NO 3 ) 2 ( 4 ) are described in this investigation [H 2 L 1 = N , N ′‐ethylenebis(3‐methoxysalicylaldimine); H 2 L 2 = N , N ′‐ethylenebis(3‐ethoxysalicylaldimine); ethylene = (CH 2 ) 2 ; propylene = (CH 2 ) 3 ; butylene = (CH 2 ) 4 ]. Compounds 2 and 3 crystallize in the orthorhombic Pcab and monoclinic C 2/ c systems, respectively, while the space group of compounds 1 and 4 is triclinic P $\bar {1}$ . In all of these four compounds 1 – 4 , the two + NH 3 sites of the [H 3 N(CH 2 ) n NH 3 ] 2+ dication ( n = 2–4) behave as guests in the O 4 compartment of two [Cu II L 1 /L 2 ] moieties through bifurcated N–H ··· O(phenoxo) and N–H ··· O(methoxy/ethoxy) hydrogen‐bonding interactions. Evidently, two mononuclear copper(II) moieties are interlinked by bridging supramolecular synthons, resulting in the formation of a supramolecular dimer in the title compounds. From the extent of displacement of the N atoms of [H 3 N(CH 2 ) n NH 3 ] 2+ from the least‐squares O(phenoxo) 2 O(methoxy/ethoxy) 2 plane, it is clear that [Cu II L 1 ] is a better host than [Cu II L 2 ] for the diprotonated diamine guests. Comparison of the inclusion of water and diprotonated diamines in [Cu II L 1 /L 2 ] is also described in the present investigation. Interestingly, of the two guest species, water and diprotonated diamines, [Cu II L 2 ] prefers the former and [Cu II L 1 ] prefers the latter.