No executor, trustee or other fiduciary may take, or refuse to take, any action, or make or retain any investment, the result of which would defeat an otherwise available marital deduction under the Internal Revenue Code (26 U.S.C.), or under the laws of this state, if the obvious and expressed intent of the testator or settlor was to take advantage of this deduction. After May 23, 1977, this section applies to all acts or investments, by all executors, trustees or other fiduciaries, as to all wills and trusts, whenever these instruments were executed or created.