archives@tulane.edu / Abstract
Condensation of 1,8,13-tris(mercaptomethyl)triptycene and tris(bromomethyl)methane yields the in,in-cyclophane 30 in 8% yield with two inwardly directed methine groups. The X-ray analysis clearly shows that it is the in,in-isomer. The proton NMR spectrum displays an obvious coupling between the two methine hydrogens, which was proved by selectively irradiation one of the apical methine proton. The coupling constant is 2.0 Hz, which is the largest through-space coupling observed so far. Based on DFT and MP2 calculations, the hydrogen-hydrogen non-bonded contact distance is estimated to be 1.50-1.53 Å.
Two in,in-cyclophanes 31 and 56, containing one or two methyl groups in their central cavities, have been synthesized, crystallized and fully characterized by ¹H and ¹³C NMR spectroscopy, MALDI-TOF mass spectrometry, IR spectroscopy, and X-ray crystallography. Cyclophane 31 is the first example of an in,in-cyclophane with a methyl group inside the cavity. The IR spectrum clearly shows that the Si-H stretch is blue-shifted from 2177 cm-1 in an acyclic model to 2269 cm-1. Based on computational studies, cyclophane 31 has a very short non-bonded H---CH3 distance of about 2.30 Å. Cyclophane 56 does not have short non-bonded contact distance, but it is the first example of a macrobicyclic compound that contains two inwardly directed methyl groups.
Three cyclophanes with the formula (C28H31PS3)n, where n = 1 or 2, were isolated from the base-promoted macrocyclization of tris(2-mercaptophenyl)phosphine and tris(3-bromopropyl)methane. Spectroscopic and X-ray analysis showed them to be the in,in-isomer 32, the in,out-isomer 60, and a dimeric in,out,in,out-isomer 61. Compounds 32 and 61 display approximately C3-symmetric and Ci-symmetric structures, respectively, in the crystal, but compound 60 adopts two distinct low-symmetry conformations in the solid state. In each case, the observed structures correspond to the lowest energy conformations of their respective isomers as calculated at the B3PW91/6-31G(d) level of theory. The in,in-isomer 32 displays a close contact between the phosphine in-lone pair and the in-methine group, with through-space spin-spin coupling constants of JPH = 9 Hz and JPC = 24 Hz, the latter of which appears to be the largest reported phosphorus-carbon through-space coupling constant.
Dodecaphenyltetracene (75), the largest perphenylacene yet prepared, was synthesized from known tetraphenylfuran, hexaphenylisobenzofuran, and 1,2,4,5-tetrabromo-3,6-diphenylbenzene in three steps. The X-ray structure of the deep red, highly luminescent 75 shows it to be a D2-symmetric molecule with an end-to-end twist of 97o. The central acene is encapsulated by the peripheral phenyl substituents, and as a result, the molecule is relatively unreactive and even displays reversible electrochemical oxidation and reduction.
Decaphenylphenanthrene (77), the first nonlinear perphenyl polycyclic aromatic hydrocarbon to be prepared so far, has been made from tetraphenylfuran and 1,2,3,4-tetrabromo-5,6-diphenylbenzene in two steps. The X-ray structure contains two independent molecules of 77, and each of them ppssesses approximate C2 symmetry in the crystal. / 1 / yonglong xiao
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_110736 |
| Date | January 2019 |
| Contributors | Yonglong, Xiao (author), Robert, Pascal (Thesis advisor), School of Science & Engineering Chemistry (Degree granting institution) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | electronic, pages: 174 |
| Rights | No embargo, Copyright is in accordance with U.S. Copyright law. |
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