Cryptands with large cavity lengths over 16 Å and N₈0₆hetero-donors: Template macrobicyclization and structure of a binuclear copper(I) cryptate

Hetero-tritopic N₈O₆ cryptands L¹ and L² were synthesized via 2 +3 silver(I) template Schiff-base macrobicyclization of tris(2-aminoethyl)amine and tris(3-aminopropyl)amine with 4,4′-methylenedioxy-dibenzaldehyde, respectively. The resulting binuclear silver(I) cryptates [Ag₂L¹](ClO₄)₂ (1) and [Ag₂L²](ClO₄)₂ (2) were characterized by various methods (elemental analyses, IR, UV-Vis, ¹H and ¹³C NMR, and FAB mass spectra). The binuclear copper(I) cryptate [Cu₂L¹I(BF₄) ₂•DMF•EtOH•H₂O (3) was synthesized by transmetallation with 1 and studied by spectroscopic and X-ray structural analyses. It crystallizes in the monoclinic, space group P2₁/n with a = 16.088(5), b = 11.941(4), C = 34.08(1) Å, β = 91.69(2)°, Z = 4. d = 1.41 g cm^-3. R₁ = 0.117, WR₂ = 0.111 (on 3859 observed with 1>2σ(I)). The bicopper(I) cryptate looks like a twisted elongated ellipsoid, possessing cavity length 16.4Å and Cu(1)⋯Cu(2) separation 12.132(5) Å. The two Cu(I) centers have similarly high stability towards oxidation. The cryptate does not show any reactivity or inclusion towards 4,4′-bipyridine, imidazole, N₃^-, Na⁺,K⁺ and NH₄⁺, mainly due to the highly effective distorted tetrahedron coordination around each Cu(I) enter and twisting among the three bridging-chains in the cryptand.