6533b7d8fe1ef96bd1269921

RESEARCH PRODUCT

Three 2,5-dialkoxy-1,4-diethynylbenzene derivatives

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description

2,5-Dieth­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene, C20H30O2Si2, (I), constitutes one of the first structurally characterized examples of a family of compounds, viz. the 2,5-dialk­oxy-1,4-bis­[(trimethyl­silyl)ethyn­yl]benzene derivatives, used in the preparation of oligo(phenyl­ene­ethynylene)s via Pd/Cu-catalysed cross-coupling. 2,5-Dieth­oxy-1,4-diethynylbenzene, C14H14O2, (II), results from protodesilylation of (I). 1,4-Diethynyl-2,5-bis­(hept­yloxy)benzene, C24H34O2, (III), is a long alk­yloxy chain analogue of (II). The molecules of compounds (I)–(III) are located on sites with crystallographic inversion symmetry. The large substituents either in the alkynyl group or in the benzene ring have a marked effect on the packing and inter­molecular inter­actions of adjacent mol­ecules. All the compounds exhibit weak inter­molecular inter­actions that are only slightly shorter than the sum of the van der Waals radii of the inter­acting atoms. Compound (I) displays C—H⋯π inter­actions between the methyl­ene H atoms and the acetyl­enic C atom. Compound (II) shows π–π inter­actions between the acetyl­enic C atoms, complemented by C—H⋯π inter­actions between the methyl H atoms and the acetyl­enic C atoms. Unlike (I) or (II), compound (III) has weak nonclassical hydrogen-bond-type inter­actions between the acetyl­enic H atoms and the ether O atoms.