The mass, coupling and width of the newly observed charged resonance Z_{c}^{-}(4100) are calculated by treating it as a scalar four-quark system with a diquark–antidiquark structure. The mass and coupling of the state Z_{c}^{-}(4100) are calculated using the QCD two-point sum rules. In these calculations we take into account contributions of the quark, gluon and mixed condensates up to dimension ten. The spectroscopic parameters of Z_{c}^{-}(4100) obtained by this way are employed to study its S-wave decays to eta _c(1S)pi ^{-}, eta _c(2S)pi ^{-}, D^{0}D^{-}, and J/psi rho ^{-} final states. To this end, we evaluate the strong coupling constants corresponding to the vertices Z_{c}eta _c(1S)pi ^{-}, Z_{c}eta _c(2S)pi ^{-}, Z_{c}D^{0}D^{-}, and Z_{c}J/psi rho ^{-} respectively. The couplings g_{Z_ceta _{c1} pi }, g_{Z_{c}eta _{c2} pi }, and g_{Z_{c}DD} are computed by means of the QCD three-point sum rule method, whereas g_{Z_{c}J/psi rho } is obtained from the QCD light-cone sum rule approach and soft-meson approximation. Our results for the mass m=(4080 pm 150)~text {MeV} and total width Gamma =(147 pm 19)~mathrm { MeV} of the resonance Z_{c}^{-}(4100) are in excellent agreement with the existing LHCb data.