Calixpyrole Lab report

Synthesis and Characterization of meso-oc-tamethylcalix(4)pyrrole and spectroscopic analysis with H-NMR and UV-Vis SpectroscopyDaniel GonzalezUniversity of Texas At Dallas 800 West Campbell Road Richardson 75080-3021.

Under guidance of Dr. Ronald Smaldone of the University of Texas at Dallas

ABSTRACT: Meso-octamethylcalix(4)pyrrole, (calixpyrrole), was synthesized using ace-tone with pyrrole and catalyzed with con-centrated sulfuric acid. The molecule was then characterize with H-NMR and IR spec-troscopy. A subsequent anion binding ex-periment was performed using Fenoxide and t-butyl Fluoride to monitor the shifts in wavelength of the UV-Vis spectrum of bound and unbound calixpyrrole. It was observed that indeed Calixpyrrole binds to anions, changing shape, changing its electronic aro-matic environment, and thus changing the measured wavelength on UV-Vis. It was de-termined that Fluoride out competes Fenox-ide for anionic binding with Calixpyrrole.

INTRODUCTION:Meso-octamethylcalix(4)pyrrole commonly

abbreviated OMCP and simply referred to a calixpyrrole is a cyclic multi pyrrole ring structure (figure 1). First synthesized by Bayer [1]in the early twentieth century, calix-pyrrole was originally designed in hopes for having medicinal purposes as a drug com-pound. More recently however, calixpyrrole has received its notoriety for its ability to act as a chelating agent and bind anionic com-pounds. Calixpyrrole’s four pyrrole rings al-low for 4 points of partial chelating attach-ment to negatively charged ions. Calixpyr-role’s disk shape will invert like a bowl to bind the anion (figure 2). This Chelating property can be altered by adding more pyr-role units to the system, or by changing the substituents on the pyrrole rings by elec-trophilic substitution reactions. These proper-ties may allow this molecule and its deriva-tives to be used to capture other molecules

as cages for selective drug delivery, or even to help isolate ionic contaminants. With these implications in mind the purpose of this experiment was then to visualize using NMR and UV spectroscopy, the changes in state of calixpyyrole when bound to anions and when in its native conformation.

(Figure 1)

Figure 1this is the structure of Calixpyyrole

Figure 2. Calixpyrrole with perspective

This is the structure of calixpyrrole with perspective added to demonstrate the bowl

shape of the molecule

Scheme 1.

METHODS:All methods were performed at the Univer-

sity of Texas at Dallas in Berkner Hall under the guidance of Dr Ronald Smaldone. Scale 4 was used to perform all mass measurements and the glassware of drawer 251-254 were utilized in synthesis. .35ml of pyrrole was measured out using a syringe and placed in a 125ml Erlenmeyer flask. .35 ml of acetone was then added to this same flask with pyr-role. 5ml of methanol was added to the flask as well. 3 drops of concentrated H2SO4 were added to the solution and immediately a milky yellow color change was noticed form an originally colorless solution. The flask was allowed to sit under the hood for 2 minutes and was then moved to an ice bath for 30 minutes. The ice bath was prepared using a 500ml beaker filled with crushed ice and wa-ter. After 10 minutes, the flask was checked once and it was noted that a yellowish grainy fine solid was forming in the flask. After the completion of the 30minutes on ice, the product was filtered using a Hirsch funnel fil-tration system and a yellow powder was re-covered. The product was allowed to dry on the filter paper and was left on a watchglass to do so. After 10minutes the product was dry and the mass was determined to

be .398grams. the powder was then trans-ferred to a screw cap reaction vial and left in the lab until the subsequent spectroscopic characterization could be performed.

UV Vis: on the following laboratory period 20ml of dichloromethane was used to dis-solve 10mg of the isolated product. The solu-tion was stored in a glass screw cap reaction vile and used to perform UV-Vis spec-troscopy. When performing the UV Vis experi-ment, quartz cuvettes were used as dimethyl chloride readily dissolves plastics making plastic cuvettes impractical.

H-NMR .069 g of the product was dissolved in .9 ml

of deuterated chloroform and a single pulse HNMR experiment was conducted using a Jeol system. And A single pulse experiment was conducted with a field strength of 270MHz.

IR:.0046g product was pelleted in .3785

grams potassium bromide to be used for IR spectroscopy. The spectrum was collected and analyzed, assigning significant peaks to the spectrum and can be found in chart (5).

RESULTS:

Chart 1. H-NMR of Calixpyrrole

Chart 1. The HNMR was successfully obtained with color coded peaks assigned to their respective positions on the molecule. The patern of the peaks obtained suggest that without doubt Calixpyr-role was indeed obtained. The hydrogens bound to the Aromatic

nitrogen of pyrrole were observed around 7ppm as a singlet which is unique tothis particular position pyrrole with no adja-

cent hydrogens. The largest, least deshielded peak appeared around 1.4 ppm and corresponded to the 8 peripheral methyl

groups resulting in a very large peak that is a singlet.

Chart 2.Uv-Vis Spectrum of Calixpyrrole

Chart 2. Depict the UV-vis of Just Calixpyrrole in dichlorometh-ane. Thwo distinct peaks appear at wavelength 237nm and 244

nm labeled in red and blue respectively.

Chart 3.Uv-Vis Spectrum of Calixpyrrole with Fenox-

ide

Chart 3Depicts the addition of Fenoxide, an anion, to the calix-pyrrole dichloromethane soltion. A small but noticeable shift

Chart 5. IR spectrum of Calixpyrrole

Chart 5. An IR spectrum was obtained for Calixpyrrole with the subsequent peaks labeled on the spectra. It could be seen that

there was a clear sharp peak in the 3500 cm-1 range correspond- ing to a N-H deshileded proton. Also there was noticeable =C-H deshileding around 3100 cm-1.

can be seen in both the predominate peaks indicated by a shift in the red and blue lines.

Chart 4 UV-vis of Calixpyrrole with Feroxine

and t-butyl Fluoride

Chart 4 depicts the addition of t-butyl Fluoride to the Clixpyrrole and Feroxine solution. All spectra are presented in this single im-age overlayed. It can be seen that there are 3 distint red and blue

bands corresponding tpo three separate wavelengths for each molecule/ molecule complex..

Chart 6.Uv-Vis of Calixpyrrole with T-butyl Fluoride

DISCUSSION:Over all the experiment was indeed suc-

cessful. Upon analysis of the IR and H NMR spectrum it could be seen that Cali pyrrole was indeed synthesized due to singlets at 7ppm corresponding to an isolated proton in an aromatic system, and a very large peak at 1.4 corresponding to the protons in the pe-ripheral methyl groups that are isolated from any adjacent protons. These groups were confirmed of the IR spectrum by finding a sharp peak around 3500cm-1that corresponds to a proton bonded to and deshileded by a nitrogen as well as peaks that were repre-sentative of double bonds. The UV-Vis experi-ment did not go as well as anticipated and had to be repeated on a subsequent day in laboratory. First, issues arose with the UV-Vis spectrophotometer that resulted in very strange spectra that were showing no shifts. After maintenance inspected the machine it was determined that the concentrations be-ing used were a tad high and that the blank was being placed in the wrong slot for the cuvette holder. This issue was corrected and spectra were obtained showing changes in the wave length as different anions were added. The change in wave length is due to the different electronic environments adopted by changing the shape of the pi sys-tems in the aromatic rings of Calixpyrrole.

Fenoxide is a anion and was quickly chelated by Calixpyrrole showing a shift in wave-length. This effect was then overridden by T-butyl Fluoride which will outcompete the fenoxide in binding and result in a shape (and thus wavelength) different than both calixpyrrole alone and calixpyrrole chelated to fenoxide.

In conclusion, it was observed that differ-ent anions are indeed bound by calixpyrrole and they do in fact alter the shape and elec-tronic structure of the molecule. This phe-nomena has led many researchers to begin investigating to what extent and with what selectivity can calixpyrrole derivative be ma-nipulated to chelate anionic compounds. These inquiries may lead to possible drug compound cages for selective delivery or other interesting matters of the sort.

REFERENCES1. Bayer, A Ben. Dtch. Chem.1886,19. 2184-2185

2. Ryuhei Nishiyabuet et all, Synthesis Struc-ture Anion Binding and Sensing by Calix[4]pyrrole Isomers, J. AM. CHEM. SOC. 2006, 128 , 11496-11504

3..Shriver James a, Calix[4]pyrrole: Synthesis and Anion-Binding Properties J. Chem. Ed., 2006, 89, 1330-1331