  Gabor frames play a vital role not only modern harmonic analysis but also in
several fields of applied mathematics, for instances, detection of chirps, or
image processing. In this work we present a non-trivial generalization of Gabor
frames to the quaternionic case and give new density results. The key tool is
the two-sided windowed quaternionic Fourier transform (WQFT). As in the complex
case, we want to write the WQFT as an inner product between a quaternion-valued
signal and shifts and modulates of a real-valued window function. We
demonstrate a Heisenberg uncertainty principle and for the results regarding
the density, we employ the quaternionic Zak transform to obtain necessary and
sufficient conditions to ensure that a quaternionic Gabor system is a
quaternionic Gabor frame. We conclude with a proof that the Gabor conjecture do
not hold true in the quaternionic case.
