TY - JOUR
T1 - Unusual Methylenediolate Bridged Hexanuclear Ruthenium(III) Complexes
T2 - Syntheses and Their Application
AU - Rajpurohit, Jitendrasingh
AU - Upadhyay, Apoorva
AU - Das, Chinmoy
AU - Dubey, Richa
AU - Vaidya, Shefali
AU - Krishnan, Vinoth
AU - Kumar, Ashutosh
AU - Shanmugam, Maheswaran
N1 - Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/12/3
Y1 - 2018/12/3
N2 - Three structurally analogous hexanuclear ruthenium(III) complexes were isolated with the general molecular formula of [Ru 6 III (O) 2 (μ 4 -η 2 -η 2 -CH 2 O 2 )(t-BuCO 2 ) 12 (L) 2 ] where L = pyridine (1) or 4-dimethylamino pyridine (DMAP; 2) or 4-cyanopyridine (3). Complexes 1 and 3 were solved in the tetragonal I4c2 and P4 1 2 1 2 space group, respectively, while 2 crystallized in the monoclinic system with P2 1 /c space group. In all three complexes, two oxo-centered Ru(III) triangles were bridged by a unique and a rare methylenediolate (CH 2 O 2 ) 2- ) ligand. This (CH 2 O 2 ) 2- group is reported to be an intermediate, which is not isolated in its metal-free form, to date, as it is unstable. Control experiments performed evidently reveal that the unique reaction condition followed is mandatory to isolate 1-3 and the origin of (CH 2 O 2 ) 2- is unknown at the moment, as no precursor was used to form this intermediate. The presence of (CH 2 O 2 ) 2- identified through X-ray diffraction was further unambiguously confirmed by various 1D ( 1 H and 13 C) and 2D-NMR (HSQC, TOCSY, NOESY, and DEPT) spectroscopies. Direct current (dc) magnetic susceptibility measurements performed on 1 and 2 reveal the predominant antiferromagnetic exchange interaction between the Ru(III) centers result in a diamagnetic ground state at 2.0 K. The paramagnetic influence of 1-3 at room temperature evidently felt by the 1 H nuclei of the (CH 2 O 2 ) 2- unit predominates compared to other NMR active nuclei in the complexes. The presence of an electron donating or withdrawing substituent on the terminal pyridine results in significant change in the dihedral angle of two oxo-centered triangular (Ru 3 O) planes. The change in the structural parameters of 1-3 due to the substituents markedly reflected on the absorption profile and redox behavior, which are systematically investigated. Preliminary galvanostatic charge/discharge cycling experiments performed on a representative complex (3) suggest that 3 can be a promising candidate to employ as an effective multiple electron charge carrier in a nonaqueous redox flow battery.
AB - Three structurally analogous hexanuclear ruthenium(III) complexes were isolated with the general molecular formula of [Ru 6 III (O) 2 (μ 4 -η 2 -η 2 -CH 2 O 2 )(t-BuCO 2 ) 12 (L) 2 ] where L = pyridine (1) or 4-dimethylamino pyridine (DMAP; 2) or 4-cyanopyridine (3). Complexes 1 and 3 were solved in the tetragonal I4c2 and P4 1 2 1 2 space group, respectively, while 2 crystallized in the monoclinic system with P2 1 /c space group. In all three complexes, two oxo-centered Ru(III) triangles were bridged by a unique and a rare methylenediolate (CH 2 O 2 ) 2- ) ligand. This (CH 2 O 2 ) 2- group is reported to be an intermediate, which is not isolated in its metal-free form, to date, as it is unstable. Control experiments performed evidently reveal that the unique reaction condition followed is mandatory to isolate 1-3 and the origin of (CH 2 O 2 ) 2- is unknown at the moment, as no precursor was used to form this intermediate. The presence of (CH 2 O 2 ) 2- identified through X-ray diffraction was further unambiguously confirmed by various 1D ( 1 H and 13 C) and 2D-NMR (HSQC, TOCSY, NOESY, and DEPT) spectroscopies. Direct current (dc) magnetic susceptibility measurements performed on 1 and 2 reveal the predominant antiferromagnetic exchange interaction between the Ru(III) centers result in a diamagnetic ground state at 2.0 K. The paramagnetic influence of 1-3 at room temperature evidently felt by the 1 H nuclei of the (CH 2 O 2 ) 2- unit predominates compared to other NMR active nuclei in the complexes. The presence of an electron donating or withdrawing substituent on the terminal pyridine results in significant change in the dihedral angle of two oxo-centered triangular (Ru 3 O) planes. The change in the structural parameters of 1-3 due to the substituents markedly reflected on the absorption profile and redox behavior, which are systematically investigated. Preliminary galvanostatic charge/discharge cycling experiments performed on a representative complex (3) suggest that 3 can be a promising candidate to employ as an effective multiple electron charge carrier in a nonaqueous redox flow battery.
UR - http://www.scopus.com/inward/record.url?scp=85057602076&partnerID=8YFLogxK
U2 - 10.1021/acs.inorgchem.8b02780
DO - 10.1021/acs.inorgchem.8b02780
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C2 - 30418745
AN - SCOPUS:85057602076
SN - 0020-1669
VL - 57
SP - 14967
EP - 14982
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 23
ER -