Examining the Construction of Potential Coordination Polymers with Aromatic N-oxides of Mercury(II) Michael Tran, Will Lynch and Cliff Padgett Department of Chemistry and Physics Armstrong Student Scholars Symposium April 21, 2016
Examining the Construction of Potential Coordination Polymers
with Aromatic N-oxides of
Mercury(II)
Michael Tran, Will Lynch and Cliff Padgett
Department of Chemistry and Physics
Armstrong Student Scholars Symposium
April 21, 2016
Coordination Polymers & N-oxides
• Supramolecular chemistry is a growing field of
interest
• Unique topologies and potential applications
• Applications such as gas storage, ion exchange
processes for remediation, heterogeneous
catalysis
• N-oxides: Variability of construction allows for
multiple binding modes and investigation of steric
and electronic effects
• Solid State Sciences, 2011, 13, 1692-1700.
Example Binding Modes of Aromatic N-oxides
Single Crystal X-ray Crystallography
General Synthetic Scheme
Pyridine N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.673
Hg1 – Br1 2.445
Hg1 – Br2 2.459
Bond Angle (°)
Br1 – Hg1 – Br2 159.38
Br1 – Hg1 – O1 96.62
Br2 – Hg1 – O1 89.10
Pyridine N-oxide / HgBr2
Coordination Polymer
Zig-Zag 1-D Polymer with N-oxide Bridges
2 terminal bromides per Hg
Hg:N-oxide 1:1
3-Picoline N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.702
Hg1 – Br1 2.435
Hg1 – Br2 2.448
Bond Angle (°)
Br1 – Hg1 – Br2 160.05
Br1 – Hg1 – O1 98.41
Br2 – Hg1 – O1 88.58
3-Picoline N-oxide / HgBr2
Coordination Polymer
Zig-Zag 1-D Polymer with N-oxide Bridges
2 terminal bromides per Hg
Hg:N-oxide 1:1
4-Picoline N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.542
Hg1 – Br1 2.462
Hg1 – Br2 2.449
Bond Angle (°)
Br1 – Hg1 – Br2 163.88
Br1 – Hg1 – O1 92.73
Br2 – Hg1 – O1 95.81
4-Picoline N-oxide / HgBr2
Coordination Polymer
Braided Polymer with Br- and N-oxide Bridges
1 bridging bromide, 1 terminal bromide per Hg
Hg:N-oxide 1:1
4-Methoxypyridine N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.531
Hg1 – Br1 2.462
Hg1 – Br2 2.445
Bond Angle (°)
Br1 – Hg1 – Br2 167.66
Br1 – Hg1 – O1 85.95
Br2 – Hg1 – O1 94.82
4-Methoxypyridine N-oxide / HgBr2
Coordination Polymer
Braided Polymer with Br- and N-oxide Bridges
1 bridging bromide, 1 terminal bromide per Hg
Hg:N-oxide 1:1
Quinoline N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.408
Hg1 – Br1 2.450
Hg1 – Br2 2.460
Bond Angle (°)
Br1 – Hg1 – Br2 157.20
Br1 – Hg1 – O1 101.43
Br2 – Hg1 – O1 101.23
Quinoline N-oxide / HgBr2
Coordination Polymer
Braided Polymer with Alternating Br- and N-oxide Bridges
1 bridging bromide, 1 terminal bromide per Hg
Hg:N-oxide 1:1
Isoquinoline N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.768
Hg1 – Br1 2.438
Hg1 – Br2 2.447
Bond Angle (°)
Br1 – Hg1 – Br2 160.11
Br1 – Hg1 – O1 96.56
Br2 – Hg1 – O1 90.01
Isoquinoline N-oxide / HgBr2
Coordination Polymer
1-D Polymer with N-oxide Bridges
2 terminal bromides
Hg:N-oxide 1:1
6-Methoxyquinoline N-oxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.630
Hg2 – O1 2.491
Hg1 – Br1 2.438
Hg1 – Br2 2.429
Hg2 – Br3 2.455
Bond Angle (°)
Br1 – Hg1 – Br2 178.35
Br1 – Hg1 – O1 88.27
Br2 – Hg1 – O1 93.36
Br3 – Hg2 – O1 96.09
6-Methoxyquinoline N-oxide / HgBr2
Coordination Polymer
Double Braided Polymer with Br- and N-oxide Bridges
1 bridging bromide, 1 terminal bromide per Hg
Hg:N-oxide 2:1
2,2’-Dypyridyl N,N’-dioxide / HgBr2
Bond Length (Å)
Hg1 – O1 2.472
Hg1 – O2 2.459
Hg1 – Br1 2.474
Hg1 – Br2 2.474
Bond Angle (°)
Br1 – Hg1 – Br2 158.30
Br1 – Hg1 – O1 104.97
O1 – Hg1 – O2 71.90
Br2 – Hg1 – O2 99.95
2,2’-Dypyridyl N,N’-dioxide / HgBr2
Monomer Bidentate Chelate
Monomer with π-π StackingHg:N-oxide 1:1
2,2’-Dypyridyl N,N’-dioxide / HgCl2
Bond Length (Å)
Hg1 – O1 2.458
Hg1 – O2 2.472
Hg1 – Cl1 2.334
Hg1 – Cl2 2.339
Bond Angle (°)
Cl1 – Hg1 – Cl2 161.45
Cl1 – Hg1 – O1 103.63
O1 – Hg1 – O2 70.97
Cl2 – Hg1 – O2 99.02
2,2’-Dypyridyl N,N’-dioxide / HgCl2Monomer Bidentate Chelate
Monomer with π-π StackingHg:N-oxide 1:1
Data Summary
Compound Hg-O (Å)
Hg-Br (Å)
Br-Hg-Br (°) Hg : N-oxide
Description
PNO 2.67 2.45 160 1:1 Zig-Zag N-oxide Bridge
3MePNO 2.70 2.44 160 1:1 Zig-Zag N-oxide Bridge
4MePNO 2.54 2.46 164 1:1 Braided Br- & N-oxide
Bridges
4MeOPNO 2.51 2.46 168 1:1 Braided Br- & N-oxide
Bridges
QNO 2.41 2.45 157 1:1 Braided Br- & N-oxide
Bridges
iQNO 2.77 2.44 160 1:1 Zig-Zag N-oxide Bridge
6MeOQNO 2.63,
2.49
2.44 178 2:1 Double Braided Br- & N-
oxide Bridges
2,2’-DPNO 2.46 2.47 158 1:1 Chelate Monomer
2,2’-DPNO 2.46 2.33* 161 1:1 Chelate Monomer
* Chloride
Conclusions
•N-oxide monomeric ligands are effective ligands
for forming O-Hg-O coordination polymers
•Bromide is capable of serving as both bridge and
terminal ligands in these systems
•N-oxide ligands with chelate ligand
environments for monomers
• For PNO substituted N-oxides, the Hg-O bond
length follows a general Hammett trend
•The bulkier the ligand the more “sophisticated” the
polymeric chain
•The polymers form with a general organic (π-π)
stacking layer and a inorganic layer