Jochen Ahrendt

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

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)A, 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)A, 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)A, α= 105.69(4), β= 111.10(6), γ= 86.37(6)°, R= 0.053 for 2 686 observations.

Crystal and molecular structure of the H-bonded complex between 1-chloro-2-hydroxynaphthalene-3-carboxylic acid and dimethylformamide (1∶1)

Crystal structure determination of the title complex reveals that the dimethylformamide solvent is bound to the carboxylic function of the hydroxy acid, in the form of a 7-membered hydrogen-bonded loop involving both the expected O-H⋯O and an apparently weak C-H⋯O interaction between host and guest. There is a strong intramolecular hydrogen bond between the phenolic OH and the carbonyl oxygen. Close packing of the complex units is afforded by a herringbone type alignment of host molecules.

Enclave inclusion of nitromethane by a new crown host. X-Ray crystal structure of the inclusion complex and host selectivity properties

A 21-membered macroring (1) incorporating as characteristic building blocks a 2,6-bridged pyridino site and three adjacent catechol moieties is shown to form selectively an inclusion complex with nitromethane, the crystal structure of which demonstrates a completely encapsulated guest molecule.

Crystalline inclusion compounds of tetrabenzo-18-crown-6 with uncharged organic molecules. Solid-state structure of the nitroethane complex

Tetrabenzo-18-crown-6 (1) shows distinct solid-state inclusion properties towards a number of OH-acidic, CH-acidic and low-polar uncharged organic molecules. The single crystal X-ray analysis of the inclusion complex between1 and EtNO2 (1∶1) is reported. Crystals are monoclinic,P21/c, witha=12.887(1),b=19.365(2),c=10.776(1) Å, β=96.33(2)o,Dc=1.321g cm−1,Z=4. The host macroring has a conformation similar to a ‘dentists-chair’. The complex is stabilized mainly by C−H...O type interactions involving the methyl group of the EtNO2 guest molecule which is highly disordered. The nitroethane guests are trapped in channels formed by the host macrocycles.

Selective clathrate formation with the new host systems cis- and trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid: inclusion properties and X-ray structure of an encapsulated acetic acid dimer

2 + 4 Cycloaddition of fumaric or maleic acid to anthracene produces the novel host molecules (1) and (2)respectively, which readily form inclusion compounds with a variety of solvents, among which acetic acid, as demonstrated by its crystal structure, give true clathrate formation with encapsulated dimeric guest units.