Unusual host properties. X-Ray structures of three salt-like crystalline aggregates of 1,1′-binaphthyl-8,8′-dicarboxylic acid

Abstract

In contrast with 1,1′-binaphthyl-2,2′-dicarboxylic acid (1), isomeric 1,1′-binaphthyl-8,8′-dicarboxylic acid (2) does not form inclusion compounds with aprotic or proton-donor organic molecules. Instead, salt-like associations of (2) with basic components such as pyridine, derivatives of pyridine, or related heterocycles are readily obtained, and recrystallization of (2) from pyridine in the presence of other non-basic solvents, including cyclic ethers, dipolar aprotic compounds, and acids, gives, crystalline ternary complexes. Crystal structures of the two-component aggregates (2)·pyridine (1:1) and (2)·3-(hydroxymethyl)pyridine, (1:1) and of the ternary crystal aggregate of (2)·pyridine-acetic acid (1:1:1) have been studied by X-ray diffraction. In the crystals of (2)·pyridine (1:1) and (2)·pyridine·acetic acid (1:1:1), the structures are built up from finite blocks of H-bonded (2)·pyridine and (2)·pyridine·acetic acid associations. In the case of (2)·3-(hydroxymethyl)pyridine (1:1) the side-chain hydroxy group of the pyridine moiety acts as a proton donor to the carboxyl group of a neighbouring molecule of (2), thus forming infinite undulating chains in the crystallographic c-direction. A characteristic feature of these structures is the intramolecular H bond between the carboxylic groups of (2), which works against the net bulkiness of the molecule and thus seems to result in the modest clathrate-forming ability of this host. Crystal data for (2)·pyridine (1:1): monoclinic (P2₁), a= 8.080(1), b= 17.254(2), c= 7.715(1)Å, β= 106.28(3)°, R= 0.049 for 1 860 reflections; for (2)·3-(hydroxymethyl)pyridine (1:1): orthorhombic: (Pbca), a= 15.426 7(4), b= 21.189 5(6), c= 13.372 7(4)Å, R= 0.049 for 2 085 reflections; and for (2)·pyridine·acetic acid (1:1:1): triclinic (P), a= 14.525(6), b= 10.481(4), c= 8.862(4)Å, α= 105.69(4), β= 111.10(6), γ= 86.37(6)°, R= 0.053 for 2 686 observations.