For which of the elements the sublimation enthalpies are much less?

V and Cr Fe and Co Cr and Mn Mn and V

Mn and V

The E∘(M2+/M) values are not regular which can be explained from the irregular variation of ionisation enthalpies (Δi​H1​+Δi​H2​) and also the sublimation enthalpies which are relatively much less for manganese and vanadium.