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|Section2= }} Cyclam (1,4,8,11-tetraazacyclotetradecane) is an organic compound with the formula (NHCH2CH2NHCH2CH2CH2)2. It is a white solid that is soluble in water. The compound is notable as a macrocyclic ligand, which binds strongly to many transition metal cations.〔 The compound was first prepared by the reaction of 1,3-dibromopropane and ethylenediamine.〔J. van Alphen "On Aliphatic Polyamines IV" Rec. Trav. Chim. Pays-Bas 1937, volume 56, 343–350.〕 The compound features four secondary amines. Its complexes therefore can exist as several diastereomers, depending on the relative orientation of the N-''H'' centres. Its complexes feature alternating five- and six-membered chelate rings. The closely related ligand cyclen ((CH2CH2NH)4) forms only five-membered C2N2M chelate rings and tends not to form square-planar complexes. ==N-Alkyl derivatives== Metal-cyclam complexes are prone to oxidative degradation, which is initiated by deprotonation of the secondary amine. This flaw led to the development of cyclam derivatives wherein the NH centres are replaced by tertiary amines. For example the tetramethyl derivatives are readily prepared by methylation using formaldehyde and formic acid.〔E. Kent Barefield "Coordination chemistry of N-tetraalkylated cyclam ligands—A status report" Coordination Chemistry Reviews 2010, volume 254, pages 1607–1627.〕 These oxidatively robust derivatives of cyclam have enabled a number of metal-dioxygen complexes.〔J. Cho, R. Sarangi and W. Nam, "Mononuclear Metal-O2 Complexes Bearing Macrocyclic N-Tetramethylated Cyclam Ligands", Accounts of Chemical Research 2012, 45, 1321-1330. 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cyclam」の詳細全文を読む スポンサード リンク
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