Complexing of carbohydrates with copper ions: A reappraisal

Contrary to statements in the literature, Cu2+ ions form only weak complexes with polyols. At pH > 5, however, strong complex formation is observed which is attributed to [Cu2(OH)2]2+ or similar binuclear ions. The formation of tetradentate complexes is postulated with compounds having four hydroxyl groups in suitable steric relationship, especially alditols.