Saturday, March 31, 2012


As I alluded to in my previous post, this summer I will be researching Metallacrowns at the University of Michigan. In this post, I will describe some of the things I will be doing in my 10 weeks in Ann Arbor. I apologize ahead of time if many of the things I am about to discuss are difficult to grasp. Unless you’ve taken a year of general, organic, and inorganic chemistry, much of the terminology/topics will be hard to grasp, but I’ll try to make up for this by adding a few visuals.
First of all Metallacrowns are inorganic analogues of crown ethers, which have –[C-C-O]n- repeating units. Metallacrowns introduce transition metals into the backbone and have –[M-N-O]n- repeating subunits, where M is a transition metal.
This field of chemistry was discovered accidently In 1989, the Pecoraro group was studying salicylhydroximate-vanadium complexes and found out that they accidently synthesized the first Metallacrown – they made something they weren’t expecting to! Here are a few examples of the structures of these molecules, which have been characterized using x-ray crystallography. 
Compared to their organic counterparts (cyclic ethers, macrocycles, cryptands, etc…) they are much easier to synthesize, are produced in high yields using common lab solvents (very cost effective!). The inclusion of transition metals also eliminates structural restrictions. New geometries such as octahedral (the classic geometry seen in coordination chemistry) and trigonal bipyramidal become accessible and allow one to build complex structures in two and three dimensions. 
All of this would be worthless unless Metallacrowns could be applied in practical ways. Currently, they’re being used as encapsulation and molecular recognition agents (think removal of heavy metals in lakes and streams), single molecule magnets, liquid crystals, and antibacterial compounds, to name a few. 
This summer I will be attempting to implement some previously made Metallacrowns into Rotaxanes, which are like a molecular ring and axle. We hope to incorporate these new molecules into molecular machines, drug delivery devices, and stimuli responsive materials.
I’ll also be introduced to many new instrumental and analytical techniques that aren’t available at Drake, including: electrospray mass spectrometry, 1H NMR, and x-ray diffraction/crystallography. It’ll be an exciting 10 weeks to discover if a career in research and pursuing graduate school is right for me!

This Metallacrown has encapsulated a Lanthanide ion

A 3-D complex with three encapsulated metals

1 comment:

  1. Hey Michael,
    This is Christian, and I will be seeing you this summer at Michigan. I really enjoy reading your blog, and your thoughts on everything.
    I look forward to meeting you this summer. :)