Abstract
The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2743-2747 |
| Number of pages | 5 |
| Journal | Tetrahedron |
| Volume | 37 |
| Issue number | 16 |
| DOIs | |
| State | Published - 1981 |
| Externally published | Yes |
ASJC Scopus subject areas
- Biochemistry
- Drug Discovery
- Organic Chemistry
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In: Tetrahedron, Vol. 37, No. 16, 1981, p. 2743-2747.
Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Conformational analysis of mesocyclic polythioethers. Gas phase conformational analysis of five mesocyclic polythioethers using photoelectron spectroscopy
AU - Setzer, William N.
AU - Coleman, Brian R.
AU - Wilson, George S.
AU - Glass, Richard S.
N1 - Funding Information: solid state, as determinedb y X-ray” and neutron dissolvedin eithercarbondisulfideor chloroformT.he diffraction”’ and in the gas phasea s determinedb y solidstateIRspectraforboth1,CDTCHand l,S-DTCN, photoelectronsp ectroscopy?F orce field calculations on theotherhand,aresimilarto thesolutionIR spectra. also indicatet he crown conformationto be the most stable.41 CONCLUSIONS The X-ray crystals tructureo f I,S-DTCN indicateda Comparisono f the orbitale nergyl evelsc alculatedb y 1333o1r twist-boat-chacior nformatioonf Cz symmetryin variouss emi-empiricaMl O methodsw ith the gas phase the solid state.T he molecularm echanicsc alculations photoelectrosnp ectrao f severalm esocyclicp olythio-also indicatet his conformationto be the most stable etherst,o gethewr ithm oleculamr echaniccso nformational (Fig. 4). The calculatedS lone pair splittingsf or this analysis,h as madei t possiblet o assignt he gas phase conformationa re in excellenta greemenwt ith a PES conformationso f 1, CDTCH, I ,5-DTCN, I ,4,7-TTCN, (0.10a nd 0.05eV respectivelyfo r EH and CNDO/Z, 1,6-DTCD,a nd tentativelyI JDTCO. The twist-chair comparedto 0.1e V observed)H. oweverM, INDO/3 cal-conformatioonf C2s ymmetrayd optedb y 1,4-DTCHa nd culationsw, ith geometryo ptimizationg,i vea somewhat the twist-boat-chair[3, 33],c onformationsa doptedb y larges plittingo f 0.35e V. This larges plittings eemsto be 1,5-DTCNa nd I ,4,7-lTCN in theg asp hasea ret hes ame due to a significantlys mallert ransannulaSr-S distance conformationass found in the solid state.A lthought he from MIND0/3 (3.63A ) thanf rom MM1 (4.00A ) or the conformationo f I,6-DTCD is a boat-chair-boabto th in X-ray crystals tructure(4 .11A ).‘” the gas phasea nd solid state,t he S atomso ccupyc on-X-ray crystals tructurea nalysish ass hown1 ,4,7-TTCN formationalldy ifferents itesi n thet wo states. to adopta symmetrica[l3 33]c onformationin the solid The techniqueo f using molecularm echanicso r state.” Molecularm echaniccs alculationsh, oweveri,n - MIND0/3 calculationsfo r geometryo ptimizationa nd dicatet he[ 12222c1o nformatioonf Cz symmetry(F ig. 5) evaluationo f thec onformationaeln ergieso f mesocyclic to be mores tableb y 2.30k cal/moleT. he photoelectron polythioethercs,o upledw ith the use of semi-empirical spectrumof l,4,7-‘ITCN showst hes ulfurl onep airo rbi-MO methodfso r comparisown ithp hotoelectrosnp ectra, talst o be spliti nto two bandso f intensityr atio2 : 1.T his providesa reasonablyu sefulm ethodfo r gasp hasec on-result is in qualitativea greemenwt ith what would be formationaal nalysis.H owever,f or certainc asesM M1 expectefdo r them ixingo f threee quivalenotr bitals( asi n (1,4dithianeI,, CDTCH, and I,S-DTCO) and MIND0/3 the [333]c onformationT).h is is supportebdy MINDO/3 (1,5-DTCO,t o somee xtentl ,S-DTCN, and I,6-DTCD) calculationosn the[ 333a] nd [ 12222c1o nformationTs.h e predict extremelyc lose transannularS -S distances calculationsfo r the [333]c onformationo f 1,4,7-‘ITCN whichl eadt o erroneouslyla rgem ixingo f the S-S lone indicatet wo degeneratoer bitalsa ndo neo rbitalo f lower pair orbitals. It appearst hat further theoreticaal nd energyf or the sulfur lone pairs, with a splittingo f experimentaslt udiesa re neededt o improvet he under-0.63e V (comparedto 0.6e V, observed)N. ote that the standing( or at leastp arameterizatioonf) S-S lone pair transannulaSr-S distancec alculatedb y MM1 is 3.38A , interacti0ns.t andb y MIND0/3 is 3.61c, omparetdo 3.45A observedin theX -ray crystals tructureA. ll of whicha res ignificantly shorter than the van der Waals contactd istanceo f Acknowledgments-The authors thank the National Institutes of 3.70A .‘” Health (Grant No. HL 15104) for support of this work, Dr. The conformationo f 1,6-dithiacyclodecaonbet ained Dennis L. Lichtenberger of the University of Arizona for many from an X-ray crystal structurea nalysisi s a [2323] helpful discussions, and NRCC (Lawrence Berkeley Laboratory (boat-chair-boato)f C2,, symmetry.T he molecular of the Universitv of California) for a CDC version of the MM1 mechaniccsa lculationsh,o weveri,n dicatea nother1 23231 gram. We also thank the University of Arizona Computer Center program and an’expanded Ck version of the MINDO/3 pro- conformationto be slightlym ores table( Fig. 6). These for a generous allotment of computer time. MM1 resultsa re supportedb y MINDO/3 calculations, which indicate the [2323]c onformation( B) to be 1.63k cal/molem ores tablet han (A). As in the caseo f 15-DTCO and IJ-DTCN, thec alculatedsp littingo f the sulfur lone pairs is unusuallyl arge( 0.77e V, compared with ca 0.15e V, observed)A. gain,t hisc an be attributed to the extremelyc losea rrangemenotf the sulfur atoms as calculatedb y MIND0/3 (3.38A ). However, it is clear that the boat-chair-boacto n- formationf ound in the solid stateb y X-ray diffraction techniqueiss not the conformeirn theg asp haseU. sing the solid stateg eometryo r MM1 geometryo ptimization of this conformerg ivesa splittingo f the sulfur-sulfur lone pairo rbitalsw hichi s too small.T hereforea, lthough I6-DTCD adoptsa boat-chair-boacot nformationin the gasp haseit is of typeB not typeA whichi s foundi n the crystallinem aterialT. his conclusionis supportebdy the observatiotnh att hes olids tateIR spectrumof I,6-DTCD markedlyd iffersf rom the IR spectrao f this compound
PY - 1981
Y1 - 1981
N2 - The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis.
AB - The helium I photoelectron spectra of the mesocyclic polythioethers 1,4-dithiacycloheptane (1,4-DTCH), 1,5-dithiacyclooctane (1,5-DTCO), 1,5-dithiacyclononane (1,5-DTCN), 1,4,7-trithiacyclononane (1,4,7-TTCN), and 1,6-dithiacyclodecane (1,6-DTCD) are reported. The conformations of these molecules in the gas phase are deduced from correlations of the observed spectra with semi-empirical MO calculations, as well as molecular mechanics analysis.
UR - http://www.scopus.com/inward/record.url?scp=0000108321&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0000108321&partnerID=8YFLogxK
U2 - 10.1016/S0040-4020(01)92340-3
DO - 10.1016/S0040-4020(01)92340-3
M3 - Article
AN - SCOPUS:0000108321
SN - 0040-4020
VL - 37
SP - 2743
EP - 2747
JO - Tetrahedron
JF - Tetrahedron
IS - 16
ER -