No loans, other than through the purchase of bonds, debentures, or similar obligations of the type customarily sold in public offerings, or through ordinary deposit of funds in a bank, shall be made by a corporation to its directors, officers or key persons, or to any other corporation, firm, association or other entity in which one or more of its directors, officers or key persons are directors, officers or key persons or hold a substantial financial interest, except a loan by one charitable corporation to another charitable corporation. A loan made in violation of this section shall be a violation of the duty to the corporation of the directors or officers authorizing it or participating in it, but the obligation of the borrower with respect to the loan shall not be affected thereby.