Cyclen

Cyclen

File:Cyclen.svg
Names
Preferred IUPAC name 1,4,7,10-Tetrazacyclododecane
Other names Tetraaza-12-crown-4 [12]aneN₄
Identifiers
CAS Number	294-90-6 checkY
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:37391 checkY
ChEMBL	ChEMBL19880 checkY
ChemSpider	58488 checkY
ECHA InfoCard
E number
PubChem CID	64963
UNII	964584YO2O checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI InChI=1S/C8H20N4/c1-2-10-5-6-12-8-7-11-4-3-9-1/h9-12H,1-8H2 checkY Key: QBPPRVHXOZRESW-UHFFFAOYSA-N checkY InChI=1/C8H20N4/c1-2-10-5-6-12-8-7-11-4-3-9-1/h9-12H,1-8H2 Key: QBPPRVHXOZRESW-UHFFFAOYAQ
SMILES N1CCNCCNCCNCC1 C1CNCCNCCNCCN1
Properties
Chemical formula	C8H20N4
Molar mass	172.276 g·mol−1
Appearance	White solid
Melting point	110–113 °C (230–235 °F; 383–386 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). checkY verify (what is checkY☒N ?) Infobox references

Cyclen (1,4,7,10-tetraazacyclododecane) is an aza-crown ether with the formula (CH₂CH₂NH)₄. It is a white solid. It forms coordination complexes with metal cations and is used to synthesize the chelating agent DOTA which has several medical applications. Being structurally simple, symmetrical, and polyfunctional, cyclen has been widely investigated.

Synthesis

Some syntheses exploit the Thorpe-Ingold effect to facilitate ring-formation. Illustrative is the reaction of the deprotonated tosylamides with ditosylates:

TsN(CH₂CH₂NTsNa)₂ + TsN(CH₂CH₂OTs)₂ → (TsNCH₂CH₂)₄

The resulting macrocycle can be deprotected with strong acid. Base gives the tetramine.

High dilution conditions result in a low reaction rate penalty and this disadvantage is removed in an alternative procedure starting from triethylenetetraamine and dithiooxamide to a bisamidine – also a bis(imidazoline) – followed by reduction and ring expansion with DIBAL.

Cyclen synthesis dithiooxamide method

Coordination complexes

File:CSD CIF JIKJUI.jpg

Structure of [Ni(cyclen)(OH₂)₂]²⁺. Color code: O = red, N = blue, Ni = dark blue, white = H, gray = C.

Coordination complexes of cyclen have been studied extensively. With a 12-membered ring, it tends to bind to four contiguous sites on octahedral metal centers, forming four 4-membered rings (see example figure). In contrast the larger cyclam ligand forms complexes consisting of 4 coplanar rings.

Cyclen also forms complexes of the type [Ln(cyclen)₂]³⁺ where Ln = lanthanide.