The equilibria of chemical reaction between $alpha$-Ni(rac-[14]-decane)$^{2+}$ and polar solvents(L; ANT, MFA, DMSO, DMF, and DMA) have been investigated by the spectrophotometric method at $25^{circ}C$. (The equilibrium constants($K_1$) of) the first step in ANT, MFA, DMSO, DMF, and DMA were 31.0, 27.5, 21.3 15.9, and 6.4, respectively. The smallness of equilibrium constants ($K_2$) of the second step compared with $K_1$, was observed. $alpha$-Ni(rac-[14]-dacane)$^{2+}$ + L $leftrightharpoons$ [$alpha$-Ni(rac-[14]-decane){cdot}L]$^{2+}$ : $K_1$.[$alpha$-Ni(rac-[14]-decane){cdot}L)$^{2+}$+ L $leftrightharpoons$ [$alpha$-Ni(rac-[14]-decane){cdot}$L_2$)$^{2+}$ :$K_2$. The relationship between d-d absorption energy and half-wave potential of complex ions at ACT was considered. Macrocyclic ligands increasing d-d transition energy caused half-wave potentials of Ni(II)-macrocycle to be shifted more positively. The half-wave potentials for Ni(rac-1[14]7-diene)$^{2+}$, Ni(meso-1[14]7-diene)$^{2+}$, Ni(1[14]4-diene)$^{2+}$, $alpha$-Ni(rac-[14]-decane)$^{2+}$, ${eta}-Ni(rac-[14]-decane)$^{2+}$, and Ni(meso-[14]-decane)$^{2+}$ reductions were -1.419, -1.431, -1.450, -1.473, and -1.480 (V vs. SCE), respectively. The d-d transition energies ($ u_{max},;cm^{-1}$) of the Ni(meso-[14]-decane)$^{2+}$ isomer were discussed with the dielectric constant (${varepsilon}/{varepsilon}_0$) of the various solvents, $ u_{max}(cm^{-1})$ increased with increasing ${varepsilon}/{varepsilon}_0$.