The 2800 Angstrom forbidden (1)Sigma(u)(-)<--(1)Sigma(g)(+) transition of dicyanoacetylene shows conventional vibronic origins due to the two pi(g) vibrations and a third involving the lower pi(u) vibration. For the latter we argue against a magnetic dipole mechanism and propose that the intensity is electric dipole, involving coupling to a pi* <-- n state of reduced point symmetry (C-infinitynu or less). The strongest band in the spectrum may be another such origin, but there is a competing assignment and neither meets expectations of intensities in related bands. While the vibrational structure is emphatic that the excited-state remains linear, the rotational constants extracted from the principal bands, all double-headed and violet-degraded (DeltaB(0) positive), present problems. The apparent contraction or bending of the molecule thus indicated can be countered by large corrections that yield negative values of the equilibrium constant DeltaB(e). The size of these corrections and further B values extracted from sequence bands indicate that rotational constants are not uniformly linear in the quantum numbers of the bending vibrations.