Synthesis of New Carbamate Materials from Primary Amines and CO 2

Transcription

1 Synthesis of ew Carbamate Materials from Primary Amines and C 2 Stephen Chiang University of Texas at Arlington 2006 Abstract The synthesis and characterization of novel linear polymer carbamates are reported. These unique carbamate gels are based on easily available primary amines and their reaction with carbon dioxide. They are readily formed at ambient temperatures by bubbling C 2 through solutions of corresponding primary amines in apolar organic solvents (CCl 3, hexane, MeC). 1 Resulting gels can be easily isolated from solution, dried and stored as solids refrigerated for several months. All synthesized carbamic materials were fully characterized by 1 MR spectroscopy, IR, and elemental analysis.

2 Synthesis of ew Carbamate Materials from Primary Amines and C 2 Synthesis of ew Carbamate Materials from Primary Amines and C 2 Introduction Supramolecular polymers represent a novel class of macromolecules, in which monomeric units are held together by reversible forces. 2 These polymers combine features of conventional polymers with properties, resulting from the bonding reversibility. Degree of polymerization, lifetimes, physical/mechanical properties, and their architectures can be switched on-off through the main chain self-assemblydissociation processes. The carbamate bond present in these systems, despite being covalent, is reversible and can be broken upon heating and flashing solutions with inert gases. Accordingly, as already demonstrated 3 these gels represent switchable supramolecular systems and may entrap, store and release guest molecules under the temperature, concentration and solvent choice control. Building selectivity into these systems (e.g. by means of appending specific binding sites) could dramatically increase their ability to encapsulate only selected substrates from solution and imprison them reversibly in gels. Primary amines could represent very promising building blocks for construction of such guest-selective polymers. Moreover, presence of positively charged ammonium groups in the carbamate chain opens up possibility of interaction with macrocycles such as crown ether. This feature could indicate the formation of structures known as rotaxanes (Figure 1 a,b). Rotaxanes consist of a macrocycle such as crown ether that has been threaded upon some type of chain or axle. Rotaxanes based molecular machines are of interest for their potential use in molecular electronics as logic switching elements. 4 R Fig.1a with complexed R 3 Fig.1b Model of a rotaxane Procedure A. Synthesis of ctylammonium Carbamate CCl 3 2 C 2 3-1a 1b UTA3-2

3 Synthesis of ew Carbamate Materials from Primary Amines and C 2 ctylamine (640 µl, 3.87 mmols, 1a) was added to 0.5 ml of CCl 3. C 2 gas was bubbled into the solution through a needle and the mixture was allowed to quantitatively react. nce the solution had bubbled to completion, the remaining white precipitate was placed under vacuum for 2-3 hours at room temperature, due to thermal instability, to remove any residual solvent. 5 mg of the dry 1b was redissolved in CDCl 3 and measured by 1 MR spectroscopy. B. Synthesis of Aminomethylnaphthalene Carbamate with 2 3-2a CCl 3, C 2 Complex w/ 2b Dibenzo-18-crown-6 (72.1 mg, 0.2 mmols) was added to 2 ml of CCl 3 and stirred until the solution was clear. 1 ml of the solution was transferred into another test tube containing 29µL of aminomethylnaphthalene. C 2 gas was bubbled into both solutions for approx. 3 minutes. The solution with aminomethylnaphthalene formed a precipitate, whereas the one with only crown ether remained clear. The precipitate was isolated and characterized by 1 MR spectroscopy. C. Synthesis of 1,12 Diaminododecane Carbamate C CCl n 3a 3b 1,12 diaminododecane (100mg, 0.1 mmol, 3a) was partially dissolved in 5mL of CCl 3. C 2 gas was introduced into the solution through a needle and a white precipitate immediately formed. After the C 2 gas had bubbled for 2-3 minutes the mixture was placed in a centrifuge. After decanting the solvent, the remaining solid was placed under vacuum to dry. Anal. Calcd for C : C, 63.89; 11.55;, Found: C, 63.82;, 11.56;, UTA3-3

4 Synthesis of ew Carbamate Materials from Primary Amines and C 2 With C CCl 3 3a, - 3c 10 3 Complex w/ n 1,12 diaminododecane (60 mg, 0.1 mmol 3a) was added to 6 ml of CCl 3. 1 eq of (108 mg, 0.1 mmols) was added to the solution. A white precipitate immediately formed upon bubbling of C 2. The solution was allowed to bubble for 2 minutes and later placed in the centrifuge. The solvent was removed using a pipet and the remaining solid was placed under vacuum for several hours. Approx. 5 mg of 3c was added to 0.5 ml of CDCl 3 in a MR tube. The tube was placed in a heat bath of about 60 C for 40 minutes. Some carbamate remained, but enough had decomposed for the sake of measuring MR. Results and Discussions The syntheses of the both the dimers and linear carbamates were successful and exhibited 99% yields. Appearance of a new carbonyl signal in 13C MR confirmed the presence of carbamate (Appendix G). Evidence of the presence of carbamate could also be seen in the splitting of the single C 2-2 signal in 1a into two signals of C 2-3 and C 2 - C() - in 1b(Appendix A and B). This same splitting action also occurred with the formation of 2b (Appendix C). owever, the linear polymers formed by diamines were found to be insoluble in CCl 3, DMS, DMF, Me, and 2. Therefore, elemental analysis was used to identify 3b as carbamate. The structure was further proved by IR measurement in KBr pellet. 1 MR spectra of the precipitate (carbamate materials) formed when C 2 was bubbled into solutions of monoamines 1a and 2a containing revealed the presence of the corresponding crown ether signals (Appendix D). n the other hand, when C 2 was bubbled in the solution containing only, the solution remained clear. This indicated co-precipitation of crown ether, and presumably some sort of interaction between the carbamate and. This same co-precipitation held true when a diamine like 3a was utilized. Since the obtained solid material 3c was totally insoluble, we let it decompose back to starting diamine at elevated temperatures. The resulting MR spectrum showed again the presence of corresponding crown ether signals (Appendix E). owever, MR measured after decomposition of 3c after it had been washed several times with CCl 3 did not show the signals of crown ether (Appendix F). This indicates that the interaction between carbamate and is relatively weak. A possible explanation could be the stacking of crown ether on the carbamate chain (Appendix I) occurs rather than the formation of rotaxane (Appendix ). While MR did not show any shifts of appropriate crown ether signals indicating complexation, there is some assumed interaction between crown ether and carbamates which remains to be explored and characterized. UTA3-4

5 Synthesis of ew Carbamate Materials from Primary Amines and C 2 Works Cited 1. (a) Masuda, K.; Ito, Y.; origuchi, M.; Fujita,. Tetrahedron 2005, 61, ; (b) DellPAmico, D., B.; Calderazzo, F.; Labella, L.; Marchetti, F.; Pampaloni, G. Chem. Rev. 2003, 103, ; (c) McGhee, W., D.; Riley, D.; Christ, K.; Pan, Y.; Parnas, B.; J. rg. Chem. 1995, 60, ; (d) Waldman, T., E.; McGhee, W., D. J. Chem. Soc. Chem. Commun. 1994, ; (e) Salvatore, R.,.; Shin, S., I.; agle, A., S.; Jung, K., W. J. rg. Chem. 2001, 66, ; (f) Aresta, M.; Quaranta, E. Tetrahedron 1992, 48, (g) Ito, Y; Ushitora, Tetrahedron, 2006, 62, (a) Bosman, A., W.; Sijbesma, R., P.; Meijer, E., W. Materials Today 2004, April, (b) Lehn, J.-M. Polym. Int. 2002, 51, (c) ten Cate, A., T.; Sijbesma, R., P. Macromol. Rapid Commun. 2002, 23, (d) Schubert, U., S.; Eschbaumer, C. Angew. Chem., Int. Ed. 2002, 41, (e) Brunsveld, L.; Folmer, B., J., B.; Meijer, E., W.; Sijbesma, R., P. Chem. Rev. 2001, 101, (f) Schmuck, C.; Wienand, W. Angew. Chem., Int. Ed. 2001, 40, Xu,.; Rudkevich, D., M. rg. Lett. 2005, 7, Rotaxane-encapsulated cyanine dyes: enhanced fluorescence efficiency and photostability Jonathan E.. Buston, James R. Young and arry L. Anderson Chemical Communications, 2000, (11), Acknowledgements Without the great support of the Welch Foundation for the Welch Summer Scholar Program, I would not have been able to have such a thrilling experience and gain so much knowledge. I would like to thank Dr. Rudkevich for allowing me to work in his lab. I am very grateful for my wonderful lab group that took the time to help me with my work and teach me everything I need to know. I would especially like to thank Vasek for his constant guidance. Without his help, I would not have accomplished the amount of work that I did. I also want to recognize my chemistry teacher, Mr. Ronnenkamp, for teaching me to love chemistry and giving me a strong foundation. My parents also deserve recognition for encouraging me to participate in this program and for supporting me. Praise goes to Dr. Jimmy Rogers and the counselors for their wonderful work behind the scenes. Last but not least, I want to thank my fellow Welch scholars for all the good times. UTA3-5