Axial-vector molecular structures $B_{c}^{\ast \pm} B_{c}^{\mp}$

The axial-vector molecular structure $\mathcal{M}_{\mathrm{AV}}=(B_{c}^{\ast +}B_{c}^{-} + B_{c}^{\ast - } B_{c}^{+})/2$ is explored in QCD sum rule framework. The mass and current coupling of this compound are found by means of the two-point sum rule method. It turns out that the mass of $\mathcal{M} _{\mathrm{AV}}$ is equal to $m=(12770 \pm 60)~\mathrm{MeV}$ making possible its dissociations to pairs of $J/\psi \eta_b$, $\Upsilon \eta_c$, $B_{c}^{\ast +} B_{c}^{-}$, and $B_{c}^{\ast - } B_{c}^{+}$ mesons. The partial widths of these decay modes contain the strong couplings at $\mathcal{M}_{\mathrm{AV}}$-meson-meson vertices which are calculated by utilizing the three-point sum rule method. The full decay width of the molecule $\mathcal{M}_{\mathrm{AV}}$ is formed due to these dominant processes and amounts to $\Gamma[\mathcal{M}_{\mathrm{AV}}]=(93 \pm 14)~ \mathrm{MeV}$. Our results for parameters $m$ and $\Gamma[\mathcal{M}_{ \mathrm{AV}}]$ of the hadronic molecule $\mathcal{M}_{\mathrm{AV}}$ are useful for experimental studies of various fully heavy four-quark mesons.