  We use the renormalization group method to examine the effect of phonon
mediated interaction on d-wave superconductivity, as driven by spin
fluctuations in a quasi-one-dimensional electron system. The influence of a
tight-binding electron-phonon interaction on the spin-density-wave and d-wave
superconducting instability lines is calculated for arbitrary temperature,
phonon frequency and antinesting of the Fermi surface.The domain of
electron-phonon coupling strength where spin-density-wave order becomes
unstable against the formation of a bond-order-wave or Peierls state is
determined at weak antinesting. We show the existence of a positive isotope
effect for spin-density-wave and d-wave superconducting critical temperatures
which scales with the antinesting distance from quantum critical point where
the two instabilities merge. We single out a low phonon frequency zone where
the bond-oder-wave ordering gives rise to triplet f-wave superconductivity
under nesting alteration, with both orderings displaying a negative isotope
effect. We also study the electron-phonon strengthening of spin fluctuations at
the origin of extended quantum criticality in the metallic phase above
superconductivity. The impact of our results on quasi-one-dimensional organic
conductors like the Bechgaard salts where a Peierls distortion is absent and
superconductivity emerges near a spin-density-wave state under pressure is
emphasized.
