In later life , he attempted to have Anna Maria Luisa recognized as the universal heiress of Tuscany , but Charles VI , Holy Roman Emperor , would not allow it because Florence was nominally an imperial fief , and he felt he alone could alter the Tuscan laws of succession .
In later life , he tried to have Anna Maria Luisa recognized as heiress of Tuscany , but Charles VI , Holy Roman Emperor , would not allow it .