| Research Abstract |
In this project, taking microporous coordination polymers as an example, we estimate and clarify the microscopic properties of the pores in materials on the basis of molecular orbital (M0) theory and density functional theory (DFT). Further, through molecular mechanical (MM) and monte carlo (MC) simulation, we will survey the guideline to design the coordination space by investigating the correspondence between the macroscopic and the microscopic ones.
[Results] 1) Microscopic properties of microporous coordination polymer CPL-1 On the basis of Universal Force Field (UFF), we recalibrated the force-field parameters of 02 for the purpose to describe the thermodynamic behaviors satisfactorily, e.g., the ladder structure of 02 dimers in nanochannels in CPL-1. Then, the effective potential of 02-02 interaction was expressed as V02-02, a summation of van der Waals VvdW and quadrupole interaction VEQQ. By fitting V02-02 to the ab initio data, a set of parameters D0-0, Re0-0 and q0 for an oxyg
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en atom of 02 molecule were obtained, i. e., 59.4762 K, 5.9943 a0 and -0.2227 e, respectively.
In addition, q0 could be obtained directly as -0.2518 e at the MP2/6-31G+(d) level of theory by utilizing Gaussian03, so that it could reproduce reasonably the quadrupole moment of 02 and, then, corresponds to the fitting q0 value.
2) Reaction mechanism in specific polymerization in CPL-2 It can be understood that the molecular mechanically optimized structure by using the UFF should also reproduce a specific hydrogen-bonding interaction between an methyl propiolate (MP) monomer and two oxygen atoms in the carboxylate moiety in CPL-2. The -C ≡ CH group of MP is clearly oriented towards the carboxylate oxygen atoms on the pore wall, and the acetylenic hydrogen atom and the oxygen atoms are close enough for an efficient hydrogen bonding (2.8 and 2.9 Å), which is consistent with the experimental results. A schematic illustration is shown in Ref.3 for randomly-aligned MP molecules in the nanochannel in CPL-2, which are found closely-packed in fact for controlling the stereostructure
(the cis and trans chain sequence).
[References]
(l) Y. Ohta, H. Hitomi, M. Nagaoka, R. Matsuda and S. Kitagawa, J. Amer. Chem. Soc. 2007, submitted.
(2) (a) T. Uemura, R. Kitaura, Y. Ohta, M. Nagaoka, S. Kitagawa, Angew. Chem. 2006, 118, 4218; (b) Angew. Chem. Int. Ed. 2006, 45, 4112.
(3) M. Nagaoka, Y. Ohta and H. Hitomi, Coord. Chem. Rev., 2007, 251, 2522. Less
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