Friday, October 29, 2010

3D printed buckyball

I found this model of buckyball created by the 3D printing technique through googling a few weeks ago. It is cool. One can simply print a 3D molecular structure with a 3D printer. I wonder how much it would cost to have a printer like this and how much it would cost to print a model.


It is worthy of mentioning that this model is not a beaded structure. In fact, I believe it is not possible to create a beaded structure with this kind of connectivity by using the standard beads with a single hole. The beads we normally use should represent the edges, instead of vertices of a graph.

Monday, October 18, 2010

Pentanuclear EMAC

There is a whole family of EMACs with different chain lengths and different metal atoms.
Qian-Rui made this first bead model of EMAC with five metal atoms.

The sizes of beads are 8mm and 6mm, respectively.

Wednesday, October 13, 2010

Effect of bead sizes on the pitch angle of EMACs

Here I'd to show a few photos of EMACs to how the ratio of two kind of bead sizes on the pitch angles.

1. Correct pitch angle by using 8mm and 6mm beads.

2. Ligands spiral around the central metal string too fast if we use the same kind of beads for both ligands and metal string.

3. No pitch angle if we use 10mm and 14mm beads.

Monday, October 11, 2010

Alternative weaving path of EMACs

Qian-Rui told me that it is easier to use the following weaving path for creating beaded EMACs. The one-end weaving is quite odd to me. This one uses one-end weaving for the pyridyl-groups at chain ends only.

Thursday, October 7, 2010

Weaving path for EMACs with 1,8-naphthyridine ligands

A simple weaving path for EMACs that contain 1,8-naphthyridine (萘啶) ligands:

I am not sure if Chern Chuang followed this path when he made the first beaded EMAC. Unlike EMACs with pyridyl-ligands, here one can use the same type of two-end weaving technique we used for making bead models of fullerenes.

Structure of nonanickel EMACs

Wednesday, October 6, 2010

Weaving path of EMACs

Qian-Rui told me the ingenious weaving path of EMACs he used. I made a schematic plot to show his weave path in the following figure. This path has a major difference from the ones we used for fullerenes before. I.e. one used only one end of fishing thread to weave pyridyl groups (hexagons, green) in the ligands. In doing so, he can weave the whole structure with only one long minimal fishing thread.


Qian-Rui and I discussed the possibility of using beads to build molecular models for compounds that contain hybridizations other than sp2 yesterday. We both agree that diamondoids are the best candidates. Although I knew this class of compounds for a long time. I have not thought about constructing these molecules with beads.

Here are a few beaded models of Diamondoids I just made.


Monday, October 4, 2010

Bead model of tris(bipyridine)ruthenium(II) ion

I mentioned in previous post that I tried to make a beaded model of tris(bipyridine)ruthenium(II) ion (structure is shown below), but didn't succeed.

Somehow, Qian-Rui solved the problem and just showed me the bead model he made for this molecular ion.

This model clearly shows the difference between the planar structural formula and the real 3D structure of a molecule. Chemists are quite used to draw molecules on a paper, but think actually in 3D space. The rationale is the valence shell electron pair repulsion (VSEPR) taught in most general chemistry courses.

Sunday, October 3, 2010

Soliton excitation in EMACs

Since right- and left-handed EMACs are mirror images of each other, these two conformatoins should have exactly the same energy. In other words, an infinitely long EMAC has a doubly degenerate ground states. At the absolute temperature T=0, an EMAC can stay either in the left- or right-handed conformation. But at T>0, one may have conformational fluctuations to other excited structures above the ground state. If the barrier to turn left-handed conformation to right-handed conformation is small, soliton excitation may become energetically favorable. An infinitely long EMAC with soliton (or domain wall) consists of three parts: a semi-infinitely long left- and right-handed structures on two sides of polymer and a soliton (a domain wall) with finite lengths in between. It is not easy to determine the size and creation energy of a soliton in an EMAC polymer, though.

Base on my experience with beaded EMACs, it is quite easy to make a soliton in the beaded model as shown in the following picture. So it is reasonable to assume that soliton excitation should be easy in the real, infinitely long EMAC polymers.

Metalwire stands for bead models

I bought two little metalwire stands for my beadworks from a souvenir store in the Taipei zoo, the largest zoo in Asia according to the Wikipedia.

(T120 made with 180 6mm beads and 0.6 mm nylon thread. I took this photo on the high speed railway back to Chu-Bei.)

Conformation transition from right- to left-handed EMACs?

It is quite easy to see that the beaded model is just like a rigid rod with a long persistent length. The surrounding ligands can spiral around the central axis either right- or left-handedly, corresponding to the right- or left-handed EMACs. Examining the bead model of an EMAC, one should notice that the surrounding ligands are a little bit flexible with respect to the central axis. For instance, it is not hard to turn a right-handed EMAC into left-handed EMAC. This might suggest that the same kind of transition could easily occur in the microscopic world. One way to prove that this kind of change really exists is to perform temperature-dependent NMR spectra. Hopefully, I can convince Prof. S.-M. Peng to do this experiment someday.

Two mor pictures of beaded EMAC

Two more pictures I took at Starbucks Chubei, Hsinchu, yesterday.

Saturday, October 2, 2010

Some thoughts on beaded EMACs

Two weeks passed since Chern showed me the first beaded EMAC. Qian-Rui and Chern have further demonstrated that beads can be applied to many more EMACs with different chain lengths and ligands.
I thought, maybe there are more different types of molecules, especially coordination compounds, that can be made with beads. I tried to imagine other molecules I can think of. I tried tris(bipyridine)ruthenium(II) ion tonight. But it didn't work. Right now, I couldn't find any other molecules that can be constructed with beads easily.
It is also quite surprising to me that my group (especially, Qian-Rui Huang and me) has been working on the transport properties of EMACs for a few years. Additionally there is a giant physical model of the longest EMAC compound hung in the main lobby of our deparment, which I've seen almost everyday. But I didn't realize earlier that this class of molecules can be built so faithfully with beads that we have been playing with for four years already.

Two more beaded EMACs

The other two beaded EMACs Qian-Rui made early last week are here. The sizes of beads seem to be 12mm and 8 mm. The pitch angle of the resulting four ligands is so small, so we can almost view them as in parallel with the central metal string in this case. Here Qian-Rui has also managed to add two axial ligands corresponding to the -NCS to two ends of these two molecules.

Torus C120 with Crystal Beads

Last week Qian-Rui and I went to 延平北路 for the properly sized beads that he needed to construct the beaded EMACS in the previous post. I also bought some beads made of artificial quartz and here is the results: