Oligosiloxanediols as building blocks for supramolecular chemistry: hydrogen-bonded adducts with amines form supramolecular structures in zero, one and two dimensions

Abstract

The structure of 1,1,3,3,5,5-hexaphenyltrisiloxane-1,5-diol-pyrazine (4/1), (C36H32O4Si3)4.C4H4N2 (1), contains finite centrosymmetric aggregates; the diol units form dimers, by means of O-H...O hydrogen bonds, and pairs of such dimers are linked to the pyrazine by means of O-H...N hydrogen bonds. In 1,1,3,3,5,5-hexaphenyltrisiloxane-1,5-diol-pyridine (2/3), (C36H32O4Si3)2.(C5H5N)3 (2), the diol units are linked into centrosymmetric pairs by means of disordered O-H...O hydrogen bonds: two of the three pyridine molecules are linked to the diol dimer by means of ordered O-H...N hydrogen bonds, while the third pyridine unit, which is disordered across a centre of inversion, links the diol dimers into a C3(3) (9) chain by means of O-H...N and C-H...O hydrogen bonds. In 1,1,3,3-tetraphenyldisiloxane-1,3-diol-hexamethylenetetramine (1/1), (C24H22O3Si2).C6H12N4 (3), the diol acts as a double donor and the hexamethylenetetramine acts as a double acceptor in ordered O-H...N hydrogen bonds and the structure consists of C2(2) (10) chains of alternating diol and amine units. In 1,1,3,3-tetraphenyldisiloxane-1,3-diol-2,2'-bipyridyl (1/1), C24H22O3Si2.C10H8N2 (4), there are two independent diol molecules, both lying across centres of inversion and therefore both containing linear Si-O-Si groups: each diol acts as a double donor of hydrogen bonds and the unique 2,2'-bipyridyl molecule acts as a double acceptor, thus forming C2(2) (11) chains of alternating diol and amine units. The structural motif in 1,1,3,3-tetraphenyldisiloxane-1,3-diol-pyrazine (2/1), (C24H22O3Si2)2. C4H4N2 (5), is a chain-of-rings: pairs of diol molecules are linked by O-H...O hydrogen bonds into centrosymmetric R2(2) (12) dimers and these dimers are linked into C2(2) (13) chains by means of O-H...N hydrogen bonds to the pyrazine units. 1,1,3,3-Tetraphenyldisiloxane-1,3-diol-pyridine (1/1), C24H22O3Si2.C5H5N (6), and 1,1,3,3-tetraphenyldisiloxane-1,3-diol-pyrimidine (1/1), C24H22O3Si2.C4H4N2 (7), are isomorphous: in each compound the amine unit is disordered across a centre of inversion. The diol molecules form C(6) chains, by means of disordered O-H...O hydrogen bonds, and these chains are linked into two-dimensional nets built from R6(6) (26) rings, by a combination of O-H...N and C-H...O hydrogen bonds.