Interactions of water and methanol with a mixed valence Mn(III)Mn(IV) complex are explored with H-1 electron spin echo (ESE)-electron nuclear double resonance (ENDOR) and H-1 and 2H ESE envelope modulation (ESEEM). Derivatives of the (2-OH-3,5-Cl-2-SALPN)(2) Mn(III)Mn(IV) complex are ideal for structural and spectroscopic modeling of water binding to multinuclear Mn complexes in metalloproteins, specifically photosystem II (PSII) and manganese catalase (MnCat). Using ESE-ENDOR and ESEEM techniques, H-1 hyperfine parameters are determined for both water and methanol ligated to the Mn(III) ion of the complex. The protons of water directly bound to Mn(III) are inequivalent and exhibit roughly axial dipolar hyperfine interactions (T-dip = 8.4 MHz and T-dip = 7.4 MHz), permitting orientations and radial distances to be determined using a model where the proton experiences a point dipole interaction with each Mn ion. General equations are given for the components of the rhombic dipolar hyperfine interaction between a proton and a spin coupled dinuclear metal cluster. The observed ENDOR pattern is from water protons 2.65 and 2.74 Angstrom from the Mn(III) which make an Mn(IV)-Mn(III)-H angle of similar to 160 degrees. For the alcohol proton in the analogous methanol bound complex, a 2.65 Angstrom Mn(III)-H distance is observed. Three pulse H-2 ESEEM gives best fit Mn(III)-H-2(H-1) radial distances of 3.0, 3.5, and 4.0 Angstrom for the three methyl deuterons in this complex.