  The nature of insulating state driven by electronic correlations in the
quarter-filled ladder compound $\alpha'$NaV$_{2}$O$_{5}$ is investigated within
a cluster dynamical mean-field approach. An extended Hubbard model with
first-principle tight-binding parameters have been used. It is shown that the
insulating state in the charge-disordered phase of this compound is formed due
to the transfer of spectral density and dynamical charge fluctuations where for
the latter, the role of inter-site Coulomb interaction is found to be of
crucial importance.
