Synthesis and structural studies of two pyridine-armed reinforced cyclen chelators and their transition metal complexes

TY - JOUR

T1 - Synthesis and structural studies of two pyridine-armed reinforced cyclen chelators and their transition metal complexes

AU - Wilson, Kevin R.

AU - Cannon-Smith, Desiray J.

AU - Burke, Benjamin P.

AU - Birdsong, Orry C.

AU - Archibald, Stephen J.

AU - Hubin, Timothy J.

N1 - Publisher Copyright: © 2015 Elsevier Ltd. All rights reserved.

PY - 2016/8/16

Y1 - 2016/8/16

N2 - Two novel pyridine pendant-armed macrocycles structurally reinforced by an ethyl bridge, either between adjacent nitrogens (for side-bridged) or non-adjacent nitrogens (for cross-bridged), have been synthesized and complexed with a range of transition metal ions (Co2+, Ni2+, Cu2+ and Zn2+). X-ray crystal structures of selected cross-bridged complexes were obtained which showed the characteristic cis-V configuration with potential labile cis binding sites. The complexes have been characterized by their electronic spectra and magnetic moments, which show the expected high spin divalent metal complex in most cases. Exceptions are the nickel side-bridged complex, which shows a mixture of high-spin and low spin, and the cobalt cross-bridged complex which has oxidized to cobalt(III). Cyclic voltammetry in acetonitrile was carried out to assess the potential future use of these complexes in oxidation catalysis. Selected complexes offer significant catalytic potential enhanced by the addition of the pyridyl arm to a reinforced cyclen backbone.

AB - Two novel pyridine pendant-armed macrocycles structurally reinforced by an ethyl bridge, either between adjacent nitrogens (for side-bridged) or non-adjacent nitrogens (for cross-bridged), have been synthesized and complexed with a range of transition metal ions (Co2+, Ni2+, Cu2+ and Zn2+). X-ray crystal structures of selected cross-bridged complexes were obtained which showed the characteristic cis-V configuration with potential labile cis binding sites. The complexes have been characterized by their electronic spectra and magnetic moments, which show the expected high spin divalent metal complex in most cases. Exceptions are the nickel side-bridged complex, which shows a mixture of high-spin and low spin, and the cobalt cross-bridged complex which has oxidized to cobalt(III). Cyclic voltammetry in acetonitrile was carried out to assess the potential future use of these complexes in oxidation catalysis. Selected complexes offer significant catalytic potential enhanced by the addition of the pyridyl arm to a reinforced cyclen backbone.

KW - Cross-bridged

KW - Pendant-armed

KW - Pyridyl

KW - Reinforced macrocycles

KW - Tetraazamacrocycles

UR - http://www.scopus.com/inward/record.url?scp=84960846685&partnerID=8YFLogxK

U2 - 10.1016/j.poly.2015.11.014

DO - 10.1016/j.poly.2015.11.014

M3 - Article

AN - SCOPUS:84960846685

SN - 0277-5387

VL - 114

SP - 118

EP - 127

JO - POLYHEDRON

JF - POLYHEDRON

ER -