No state can make anything but gold and silver legal tender; Congress can. No state can impair the obligation of contracts; Congress can (otherwise, all federal bankruptcy law would be unconstitutional).
Is it your contention that the framers were cool with paper money?
Hint: Not a fv&$ing chance. They had just went through a period of ruinous hyperinflation due to printed money and knew exactly the problems and temptations involved.