1. Results and Discussion
Molecular Organic Frameworks: Encapsulation effects on Diels-Alder kinetics Kassie Picard, Courtney Leo, Brady Barron, Luke Fulton, Roy Planalp Department of Chemistry, University of New Hampshire
Introduction
The color change from a pink to blue in the trial with thiophene as the guest using scaled down conditions can be rationalized by two different ideas. First, the guest molecule could be coordinating to the metal causing a color change. Second, is that the complex reacted with moisture in the air. This would explain the color change because water is a weak field ligand. UV/Vis spectra were obtained and analyzed for discrepancies in observed data.
The synthesis of the MOF crystals were carried out in test tubes with starting material in different layers. Reaction conditions were continuously changed to promote the formation of crystals (table 1). The solutions were allowed to crystalize for seven days.
Table 1. Changing reaction conditions and quantities of materials used for the synthesis of MOF crystals.
Molecular organic frameworks (MOFs) are crystalline networks of metal-ligand linkages, which form capsules in the spaces between the metals and the ligands. The complex is based on an infinite ratio of M6L4 (figure 1).
Figure 1. M6L4 infinite ligand structure forming the backbone of the MOF.1
The interstitial space is of interests to chemist, because of the stability that these spaces offer for small, unstable molecules, known as guests. MOFs can be used to store molecules (intermediates) that are reactive with their solvents, accelerate reaction rates, and “locking” a molecule in a specific configuration. These molecules have important functions in drug delivery techniques. The purpose of this project was to synthesize the MOF crystals with different guest molecules, and see the effects of the MOF structure on Diels-Alder kinetics.1
Layer A B C
Compound
Ligand
Methanol
Guest
Absolute Methanol
Co Complex
Standard- Room Temp
9.37 mg
1.5 mL
6.0 mL
0.3 mL
15.76 mg
Reaction in fridge
Reaction in Scin Vial
Scale Down
6.3 mg
1.0 mL
4.0 mL
0.2 mL
10.5 mg
No Buffer- Layer
0 mL
Decrease MeOH
No Guest C B
Figure 3. UV/Vis spectrum for the crude mixture of the ligand (1) and metal complex (2). A
Future Work
The original goal for this project was to synthesize MOF crystals and explore how the guest molecules, protected by the MOF structure, react when heated. Future work includes continued effort to synthesize the crystals by changing more reaction conditions like exposure to air and heating the samples. Once crystals are formed, they could be put on heat and the MOF broken down with acid. The guest molecules would be extracted and 1H NMR used see if any guest molecules underwent a Diels-Alder reaction.
Results and Discussion
The synthesis of MOF crystals was unsuccessful for all reaction conditions and guest molecules. This was obvious by the lack of solid, red crystals that were expected to form.2 At the start of the reaction, the layer that contained the ligand was clear, and the layer that contained the metal complex was a light pink color. The mixture of solutions was predicted to produce red crystals, but formed different colored solutions instead (table 2).
Acknowledgments
Methods
Table 2. Color change associated with MOF synthesis for each guest molecule at different reaction conditions.
Thank you to the UNH Department of Chemistry for their efforts and support during this research project.
The first part of this project focused on the synthesis of the MOF crystal using 2,4,6-tris(3-pyridal) -1,3,5-triazine (1) as the ligand and cobalt (II) thiocyanate (2) using three different guests: thiophene (3), furan (4), and toluene (5).
Guest
Thiophene
Furan
Toluene
Standard- Room Temp
Light Pink
Light Blue
Purple
Double Buffer
Lavender
Teal
Reaction in Fridge
Light pink
Reaction in Scin Vial
Dark Blue
Light Purple
Blue/Green- No solution
Scale Down
Top Light Purple/ Bottom Light Blue
No Buffer- Layer
Light purple/ pink
Decrease MeOH
Deep Blue
Rose
No Guest
Hot Pink
References
Inokuma, Y.; Yoshioka, S.; Fujita, M. A Molecular Capsule Newtwork: Guest Encapsulation and Control of Diels-Alder Reactivity. Angewandte Chemie
Zhang, M.; Lu, M.; Li, J.; Bosch, M.; Chen, Y.; Liu, T.; Liua, Y.; Zhou, H. Design and Synthesis of Nucleobase-incorporated Metal–organic Materials. Royal Society of Chemistry, Journal of Inorganic Chemistry
Plonka, A.; Chen, X.; Wang, H.; Krishna, R.; Dong, X.; Banerjee, D.; Woerner, W.; Han, W.; Li, J.; Parise, J. Light Hydrocarbon Adsorption Mechanisms in Two Calcium-Based Microporous Metal Organic Frameworks. ACS Publications .
Figure 2. Metal, ligand, and guest molecules used in the MOF synthesis.

2. Trust us to make your poster look GREAT!
This poster template provided courtesy of
UNH ESRC Poster Printing Services
Trust us to make your poster look GREAT!
Website:
Poster Guide:
DELETE THIS SLIDE BEFORE PRINTING