(E)-Diethyl 2-amino-5-(2-thienylmethyleneamino)thiophene-3,4-dicarboxylate

Abstract

The highly conjugated title compound, C15H16N2O4S2, exhibits an extended planar configuration. This unusual behavior is the result of the azomethine that adopts the E configuration concomitant with the anti­parallel orientation of the thio­phene units. The nitro­gen‐containing double bond is also ca 0.04 Å shorter than its carbon analogue.

Hydrogen-bonded network of diethyl 2,5-diaminothiophene-3,4-dicarboxylate

“…The N-C bond distances of the amine are in good agreement with those in the literature, e.g. 1.349 (3) (Skene et al, 2006), 1.345 (3) (Ç oruh et al, 2005) and 1.354 (5) Å (Ç oruh et al, 2003).…”

“…Not only do thiophenes possess desired pharmaceutical properties, they also exhibit desirable properties for functional materials, including organic light-emitting diodes (Perepichka et al, 2005) and field-effect transistors (MacDiarmid, 2001). We are interested in amino thiophenes such as the title compound, (I), because they are useful precursors in the synthesis of conjugated functional materials via Schiff bases (Skene, 2004;Skene & Trefz, 2004a,b;Dufresne & Skene, 2005a,b,c,d;Bourgeaux & Skene, 2005;Skene et al, 2006). During synthetic optimization studies, we isolated compound (I) as yellow crystals.…”

Diethyl 2,5-bis[(E)-thiophen-2-ylmethyleneamino]thiophene-3,4-dicarboxylate

“…2. For compound (II), this angle is 7.25 (11) Å (Skene et al, 2006). This is in contrast to the mean plane angle for homoaryl azomethines, which is considerably larger (65 ;Bü rgi & Dunitz, 1969).…”

The six-membered-ring azomethineN-((E)-{5-[(E)-(pyridin-3-ylimino)methyl]thiophen-2-yl}methylidene)pyridin-3-amine

“…The bond lengths for C6-N5, N5-C5 and C5-C1, as well as the bond lengths for C12-N11, N11-C11 and C11-C4 (see Table 2), are consistent with those of analogous triads consisting uniquely of thiophenes. The analogous bond lengths for (2) are 1.439 (4), 1.278 3and 1.397 (3) Å (Skene et al, 2006). The azomethine bond lengths are 0.053 Å shorter than the C C bond of analogous vinylenes (Hoekstra et al, 1975).…”

“…This is in part responsible for the observed hypsochromic shifts in the absorbance spectra of (1) relative to its all-thiophene analogue [compound (2) in the scheme]. The dihedral angles between the aryl-azomethine mean planes of (2) are 9.04 (4) and 25.07 (6) (Skene et al, 2006), and they are also smaller than for the analogous six-membered homoaryl azomethine triad,…”