  We study the light vector and axial-vector mesons. According to the
hadrogenesis conjecture the nature of the two types of states is distinct. The
axial-vector mesons are generated dynamically by coupled-channel interactions
based on the chiral Lagrangian written down in terms of the Goldstone bosons
and the light vector mesons. We propose a novel counting scheme that arises if
the chiral Lagrangian is supplemented by constraints from large-N_c QCD in the
context of the hadrogenesis conjecture. The counting scheme is successfully
tested by a systematic study of the properties of vector mesons. The spectrum
of light axial-vector mesons is derived relying on the leading order
interaction of the Goldstone bosons with the vector mesons supplemented by a
phenomenology for correction terms. The f_1(1282), b_1(1230), h_1(1386),
a_1(1230) and K_1(1272) mesons are recovered as molecular states. Based on
those results the one-loop contributions to the electromagnetic decay
amplitudes of axial-vector molecules into pseudo-scalar or vector mesons are
evaluated systematically. In order to arrive at gauge invariant results in a
transparent manner we choose to represent the vector particles by
anti-symmetric tensor fields. It is emphasized that there are no tree-level
contributions to a radiative decay amplitude of a given state if that state is
generated by coupled-channel dynamics. The inclusion of the latter would be
double counting. At present we restrict ourselves to loops where a vector and a
pseudo-scalar meson couple to the axial-vector molecule. We argue that final
and predictive results require further computations involving intermediate
states with two vector mesons. The relevance of the latter is predicted by our
counting rules.
