Electrochemical and chemical reductions of Rh-(I) complexes of L-P4 (a macrocycle containing four phosphinine rings) and of L-P2S2 (a macrocycle containing two phosphinine rings and two thiophene rings) lead, in liquid solution, to EPR spectra exhibiting large hyperfine couplings with P-31 nuclei. An additional coupling (27 MHz) with Rh-103 is detected, in the liquid state, for the spectrum obtained with [LP2S2Rh(0)]; moreover, resolved P-31 hyperfine structure is observed in the frozen solution spectrum of this latter complex. DFT calculations performed on Rh-(1) complexes of model macrocycles L'(P4) and L'(P2S2) indicate that, in these systems, the metal coordination is planar and that one-electron reduction induces a small tetrahedral distortion. The calculated couplings, especially the dipolar tensors predicted for [L'Rh-P2S2((0))], are consistent with the experimental results. Although the unpaired electron is mostly delocalized on the ligands, the replacement of two phosphinines by two thiophenes tends to increase the rhodium spin density (rho(Rh) = 0.35 for [L'Rh-P2S2((0))]). It is shown that coordination to Rh as well as one-electron reduction of the resulting complex provoke appreciable changes in the geometry of the macrocycle.