V+2/V = -1.18V, Mn+2/ Mn = - 1.18V i,e highly negative because of

The E0(M2+/M) values are not regular which can be explained fromthe irregular variation of ionization enthalpies (∆iH1+∆iH2 ) and alsothe sublimation enthalpies which are relatively much less formanganese and vanadium.