Reeived 20 Jn 2012 Aepted 19 Mr 2012 Pulished 17 Apr 2012 DI: 10.1038/nomms1793 Gint regulr polyhedr from lixrene roxyltes nd urnyl Sr Psqule 1, Sr Sttin 1, Edurdo C. Esudero-Adán 2, Mrt Mrtínez-Belmonte 2 & Jvier de Mendoz 1 Self-ssemly of lrge multi-omponent systems is ommon strtegy for the ottom-up onstrution of disrete, well-defined, nnosopi-sized ges. Ioshedrl or pseudospheril virl psids, uilt up from hundreds of identil proteins, onstitute typil exmples of the omplexity ttined y iologil self-ssemly. Chemil versions of the so-lled 5 Pltoni regulr or 13 Arhimeden semi-regulr polyhedr re usully ssemled omining moleulr pltforms with metls with ommensurte oordintion spheres. ere we report novel, self-ssemled ges, using the onil-shped roxyli id derivtives of lix[4]rene nd lix[5]rene s lignds, nd the urnyl tion 2 + 2 s metlli ounterprt, whih oordintes with three roxyltes t the equtoril plne, giving rise to hexgonl ipyrmidl rhitetures. As result, othedrl nd ioshedrl nioni metlloges of nnosopi dimensions re formed with n unusully smll numer of omponents. 1 Institute of Chemil Reserh of Ctloni (ICIQ), Avd. Pïsos Ctlns 16, Trrgon, Spin. 2 X-Ry Diffrtion nit, Institute of Chemil Reserh of Ctloni (ICIQ), Avd. Pïsos Ctlns 16, Trrgon, Spin. Correspondene nd requests for mterils should e ddressed to J.d.M. (emil: jmendoz@iciq.es). nture ommunitions 3:785 DI: 10.1038/nomms1793 www.nture.om/ntureommunitions
nture ommunitions DI: 10.1038/nomms1793 Most self-ssemled vities nd psules re sed on hydrogen onding 1 4 or oordintion hemistry 5 10, omined with vriety of liner, urved or hollow omplementry frgments to uild up three-dimensionl rhitetures, for whih the size nd numer of omponents is often diffiult to predit. For instne, in Fujit s M n L 2n (M = Pd 2 +, L = dipyridylthiophene or dipyridylfurn) gint nnosopi metlloges 11, sutle vritions in the lignd (furn versus thiophene) fvour either M 12 L 24 or M 24 L 48 rhomiuothedrl Arhimeden onstruts. In the design of hemil versions of the simpler five Pltoni solids, regulr ues or othedr require C 4 -symmetry lignd frgments to e omined with C 3 -symmetry metl ounterprts, wheres ioshedrl/dodehedrl onstruts require 12 (or 20) uilding loks of C 5 symmetry nd 20 (or 12) frgments of C 3 symmetry 8. In this ontext, roxyli id derivtives of lix[4]rene nd lix[5]rene re lignds of hoie for C 4 - nd C 5 -symmetry omponents, respetively, wheres urnyl ( 2 + 2 ) onstitutes n idel C 3 -symmetry omponent. Indeed, polyroxyltes hve een often employed s lignds for urnyl orgni frmeworks (Fs) 12 14 or moleulr ssemlies 15 17 due to the ffinity of urnyl ions for oxygen donors nd the lmost inexhustile vriety of the resulting rhitetures. A ommon geometry in urnyl roxylte [ 2 + 2 (RC ) 3 ] omplexes is hexgonl ipyrmid, in whih the three R groups of the roxylte lie in the equtoril plne, orthogonlly oriented to the pil -yl urnyl oxygens (see Fig. 1 for n exmple with enzote) 15,18,19. Although oordintion in -free lixrenes t the lower rim involving the phenol oxygens is ommon oordintion mode 20,21, we speulted tht the high symmetry nd univol formtion of polyhedrl ges would previl over other modes of oordintion. Indeed, hexmeri self-ssemled ggregtes nd psules rising from lixrenes or resorinrenes with other lnthnides nd trnsition metls hve een widely studied 22 25. ere we desrie psules 1 nd 2 rising from lix[4]rene nd lix[5]rene roxyltes nd urnyl (Fig. 1, ). A remrkle feture of these psules is tht the metls re not loted t the orners or the edges of the resulting polyhedr, like in most of the reported exmples, ut on the fes insted, offering the possiility for the inner yl oxygens to intert with guests entrpped inside the ges. Thus, the metl n t oth s gluing element for the ssemly of the omponents nd s funtionl key sustruture. Moreover, the resulting nioni psules re niely shielded strutures with lmost no windows, nd result from n unusully smll numer of omponents nd ounterions, leving sustntil mount of ville inner spe for host guest intertions. All strutures were fully hrterised oth in the solid stte (X-ry diffrtion) nd in solution (diffusion-ordered spetrosopy (DSY) MR, dynmi light sttering (DLS)). Results Solid-stte studies. Tetrformyllix[4]rene 5 ws otined s reported y Csnti t l. 26 y formyltion of lix[4]rene 3, lthough use of mirowve heting produed quntittive yields in shorter retion times. Although -lkyl lix[4]renes 9 nd 10 were esily prepred y oxidtion of the orresponding ldehydes y well-estlished proedures 27,28, oxidtion of 5 to the -free lix[4]rene 7 ws only hieved y sodium hlorite 29 in dimethylsulphoxide (DMS)/wter mixture tht prevents preipittion of oth the regents nd the prtilly oxidised intermedites. Compound 7 ws isolted in good yield y simple preipittion upon ddition of hydrohlori id. Similr onditions 1 2 1 Figure 1 Chemil strutures of urnyl ges. () The hexgonl ipyrmidl oordintion mode of urnyl with roxyltes is illustrted for enzoi id. () Chemil struture of hexmeri ge 1 from six lix[4]rene tetrroxyltes nd eight urnyl tions. () Chemil struture of dodemeri (ioshedrl) ge 2 from 12 lix[5]rene pentroxylte frgments nd 20 urnyl tions. nture ommunitions 3:785 DI: 10.1038/nomms1793 www.nture.om/ntureommunitions
nture ommunitions DI: 10.1038/nomms1793 ARTICLE C C C MTA, TFA CI 2 MW 2 P 4 n n n R 4 n = 4 3 n = 4 5 100% n = 5 4 n = 5 6 70% n = 4 7 86% R = C 3 7 9 n = 5 8 50% R = C 8 17 10 Figure 2 Syntheti sheme for the preprtion of lixrenes 5 10. All yields refer to purified produts. Strting lixrenes 3 nd 4 were otined from the orresponding p-tert-utyl derivtives ording to stndrd proedures. For syntheti detils, see Methods. were pplied with minor modifitions to lix[5]rene 4, to otin the unpreedented pentformyllix[5]rene 6 nd its oxidtion produt 8 in good-to-moderte yields (Fig. 2). Formtion of ges ws hieved in the presene of mild se suh s pyridine, whih llows deprotontion of the roxyli ids ut not of the lixrene phenol groups. In suh se, preferentil oordintion of the urnyl ion to the phenoxy groups would previl, giving to the solutions hrteristi ornge-reddish olour 30 32. Indeed, oordintion y the phenoxy groups ws oserved when stronger ses were employed, suh s esium or mmonium hydroxide, triethylmine or lrge exess of pyridine (when used s solvent). Fs re typilly otined y hydrotherml synthesis, proess tht requires high pressures nd tempertures 12 14. owever, for 1 nd 2, these hrsh onditions only produed deomposition yproduts, wheres yellow rystls suitle for single-rystl X-ry nlysis were otined t room temperture y slow diffusion of etonitrile on,-dimethylformmide (DMF) solutions of the omponents (lix[4]rene 7 or lix[5]rene 8, urnyl nitrte nd pyridine) t the required stoihiometries. Most remrkly, the strutures of these gint suprmoleulr ssemlies were resolved using in-house devies, rotting node with MoK α nd two mirosoures with MoK α nd CuK α rdition without requiring the use of synhrotron light em, s for mny other gint ssemlies 11,33. The othedrl omplex 1 (Fig. 3) rystllises in the feentred ui spe group Fm-3m showing high degree of symmetry. The inner yl oxygens of the urnyl ions define regulr hexhedron (ue) of 7.0242(15) Å edges (Fig. 3). The nioni ge is mde out from six lixrenes nd eight urnyl suunits. The rystl pking shows tht the othedr re orgnised in lose proximity, with n lmost perfet, not interpenetrted, stking of the romti wlls (t 3.54 Å distne; Fig. 3). A top view of two-dimensionl lyer (Fig. 3d) revels some spe etween every four othedr, with the lixrene groups fing the orners. Additionl lyers stk on top of eh other, in n egg-ox rrngement. Likely, this spe is oupied y disordered solvent moleules or ounterions. Eh psule requires eight tioni ounterions to lne the overll negtive hrge (one negtive hrge per urnyl suunit). In the rystl desried in Fig. 3, these tions re pyridines tht were not lolised. Thus, polytioni ounterion, suh s 1,4,7, 10-tetrzylododene (ylen, Fig. 4) tht ould fill the inner spe, ws evluted s n enpsulted guest. Two ylen moleules re neessry to lne the overll negtive hrge of eh ge. Remrkly, in the resulting rystl struture, one guest moleule is loted inside the ge, wheres nother one fits etween the orners of the hexmeri ggregtes (Fig. 4 nd ). The outer ylen moleules re stilised y hydrogen onds with the hydroxy groups of the lixrenes. When -lkyl lix[4]renes 9 nd 10 were employed, the orresponding othedrl rystl strutures 11 nd 12, nlogous to 1, were otined s well (Supplementry Figs S1 nd S2). Cge 11 spontneously rystllised in DMF, wheres rystls of struture 12 Figure 3 Solid-stte struture of the hexmeri ge 1. () Wirefrme representtion showing the ue defined y the inner yl urnyl oxygens (7.02 Å edges) nd the orresponding insried sphere representtive of n inner ville volume of. 940 Å 3. () Spe-filling representtion of the ge; () nd (d) two views of the rystl pking long the (1 1 1) diretion nd the -plne, respetively. The fes of the othedr lign in losely stked lyers (), whih disply eggs-ox shpe when 2D lyer is seen from the top (d). d required slow diffusion of etonitrile on tetrhloroethne (TCE) solution of the omponents. Although neither 10 nor urnyl nitrte re solule in TCE, the mixture of oth omponents eomes solule fter 3 dys shking in the presene of pyridine, s soon s ge 12 forms. Beuse of the presene of ulky -lkyl hins t the lower rim of eh lixrene, lose pking of the othedrl ges ws not oserved. In ge 12, ering long -otyl hins, the othedron ws slightly distorted. Pyridinium tions, lning the hrges of oth ggregtes 11 nd 12, ould e loted either inside or outside the ges. In 11, three pyridinium ounterions re loted within the fing propyl hins nd in the inner ge of the othedron digonl. In the se of ge 12, ering longer -otyl hins, four ounterions were oserved in lose pking inside the ge (together with wter moleule), wheres the remining four ounterions were outside. Another Pltoni solid, ioshedron 2 (Fig. 5), ws formed when lix[5]rene pentroxyli id 8 ws used. In this se, 12 lixrenes displying wide-open one onformtion re pled t the verties, wheres 20 urnyl ions glue the ensemle t eh of nture ommunitions 3:785 DI: 10.1038/nomms1793 www.nture.om/ntureommunitions
nture ommunitions DI: 10.1038/nomms1793 + + + + Figure 4 Crystl pking of the hexmeri ge 1 with ylen. () Tetrprotonted 1,4,7,10-tetrzylododene (ylen). () Wirefrme representtion of the hexmeri ge hosting ylen tetrtion. () Crystl pking long the xis showing one lyer of psules with ylen guests inside nd outside the ggregtes. the fes. Twenty dditionl pyridinium ions re ounterlning the negtive hrges, lthough only two were loted for eh psule, in the spe ville t the lower rim etween two spheril ggregtes. verll, the struture is mde of 32 piees nd 20 ounterions, remrkly low numer of omponents reltive to other metlloges, suh s Fujit s gint ge of slightly igger size (72 piees + 24 PF 6 ounterions) 11. If we pproximte the ge to sphere, this would hve dimeter of 3.65 nm nd n outer volume of. 25.5 nm 3. The pking is very ompt without interpenetrtion of the psules, lthough sizle holes of. 1,500 Å 3 totl volume re present etween the hydrogen-onded spheres. This rrngement is due to hydrogen onding etween the hydroxyl groups t the lower rims nd the outer yl oxygens. Two pyridinium tions ould e loted hydrogen onded to one of the outer yl oxygens (Fig. 5 nd ). o ttempts were mde to prepre onil -lkyl derivtives of lix[5]rene 8. Indeed, it hs een reported tht -enzyl lix[5]rene displys 1,2-lternte onformtion in the solid stte 34, nd longer tils, suh s otyl, produe mixtures of different onformtions 35. Solution studies. The formtion of ges 1, 2, 11 nd 12 ws lso studied in solution y MR nd DLS. 1 nd DSY MR spetrosopy t 300 K showed tht ge formtion ws highly dependent on the solvent used nd on the onentrtion of the smple. Cges 1, 2 nd 11 were nlysed in DMF d 7, wheres spetr of 12 were tken in 1/1 DMF d 7 /TCE d 2 mixture. In ll ses, it ws possile to distinguish the signls for the ge nd the free lixrene (Supplementry Figs S3, S5, S7 nd S9), reveling slow equilirium in the MR time sle (see Supplementry Tles S1 nd S2 for pprent stility onstnts). For instne, the romti proton signl of monomeri lixrene 7 t 7.80 p.p.m. slightly shifts to 7.78 p.p.m. upon ddition of urnyl nitrte, or to 7.74 p.p.m. in the presene of pyridine, s the nioni roxyltes re formed. When oth omponents re dded to the solution of monomer, the ge forms nd the monomer signl stys t 7.75 p.p.m., wheres new rod signl orresponding to the ge rises t. 8.38 p.p.m. (Supplementry Fig. S3). DSY spetr (Supplementry Fig. S4) onfirm tht ge 1 is formed only when oth urnyl nitrte nd pyridine re present long with the lix[4]rene. This rises from the ft tht only one speies diffusing slower thn the lixrene is present long with the lignd nd the solvent. A single lrge speies ws lso present in the se of lix[5]rene 8 nd ge 2, long with the monomeri lixrene (Supplementry Figs S5 nd S6). A mixture of oth ges, formed independently, did not revel signifint hnges in the DSY spetr, oth speies existing independently in equilirium (Fig. 6). Similrly, DSY spetr of ges 11 (Supplementry Fig. S8) nd 12 (Supplementry Fig. S10) show the presene of only one speies with diffusion oeffiient lower thn the lixrene lignd. Diffusion oeffiients nd hydrodynmi rdii re orrelted theoretilly y the Stokes Einstein eqution, whih requires the diffusion oeffiient to e determined t infinite dilution 36. ther ftors, suh s onentrtion, temperture, flutution, onvetion nd visosity hnges re lso influentil 37,38. In our se, these prolems ould not e hndled y mens of lirtion with n internl referene, s we were unle to find suitle stndrds of similr sizes nd shpes. For these resons, no quntittive estimtion of our ges sizes ws ttempted y DSY, nd DLS ws employed insted. nly one Gussin distriution ws oserved for eh ompound in DMF, nd the oserved hydrodynmi rdii were in full greement with the dimensions of the ges in the solid stte (Supplementry Fig. S11). Thus, for -unsustituted ges 1 nd 2, the mesured rdii were 1.226 nd 1.699 nm, respetively, whih niely fit with the 1.2- nd 1.7-nm vlues estimted from the rystl strutures. For -lkyl derivtives of the hexmeri ges 11 nd 12, the rdii were 1.236 nd 1.472 nm, onsistent with the dimensions of n othedron ut slightly smller thn the estimted rdii from the solid stte strutures (1.6 nd 2.1 nm, respetively), lthough it is likely tht lkyl hins in the polr DMF solutions do not fully extend s in the rystl. Disussion A ommon feture of the Fs is the presene of strong = onds in the liner struture of the urnyl tion, whih fores oordintion of dditionl lignds t the equtoril positions, with the yl oxygens in n lmost perpendiulr orienttion. The lk of xil oordintion fvours formtion of one-dimensionl hins or two-dimensionl sheets, ut mkes diffiult the formtion of well-orgnised nd preditle three-dimensionl strutures, in prtiulr when plnr romti lignds re employed 12. To the est of our knowledge, fullerene type, polyhedrl ges hve een desried y Burns et l. 39 from urnyl peroxide omponents 40,41, without orgni moieties involved in the ge frmework. owever, nture ommunitions 3:785 DI: 10.1038/nomms1793 www.nture.om/ntureommunitions
nture ommunitions DI: 10.1038/nomms1793 ARTICLE Figure 5 Solid-stte struture of the ioshedrl ge 2. () Wirefrme representtion showing qusi-dodehedron defined y the inner yl urnyl oxygens with edges etween 8.24 nd 9.07 Å, nd n insried sphere of. 12 Å rdius (7238 Å 3 volume), representtive of the inner ville spe. () Position of the pyridinium ounterions interting with the oxygen of the urnyl nd wter moleule hydrogen onded to n group of the lower rim. () View of the rystl pking. The vity is likely filled with disordered pyridinium tions nd solvent moleules. use of owl-shped lixrene roxyli ids llows ssemly into defined nd unique gloulr ssemlies, uilt up from orgni lignds nd urnyl, in whih the urnyl groups re entred in the fes of regulr polyhedr. We hve shown tht lix[4]renes promote self-ssemly into hexmeri ges, wheres lix[5]rene gives rise to ioshedrl strutures, with remrkle eonomy in the numer of orgni lignds required for the ssemly. Thus, hexmeri ges with n ville spheril volume of.940 Å 3 inside the inner yl oxygens re otined with six lix[4]rene frgments, wheres dodemeri ge with n ville volume of more thn 7000 Å 3 results from the ssemly of only 12 lix[5]rene suunits. The vities of the lixrene suunits re oriented towrds the entre of the ge, so the overll inner volume is mximised. Consequently, the lower rim of eh lixrene protrudes wy from the vity, ontriuting to the stility of lose-pked, non-interpenetrted, hydrogen-onded three-dimensionl network in -free lixrenes, or to the soluility of the ggregtes in orgni solvents in the se of -lkyl derivtives. The lixrene urnyl psules desried here re nioni, in ontrst to most of the so-fr reported metllo-psules. As eh urnyl suunit ontriutes one negtive hrge to the overll struture, the numer of ounterions needed is lso limited, mking the vities idelly tilored for the enpsultion of polytioni or eletron-defiient guest moleules. Fs re photoluminisent nd simultneously exhiit interesting phototlyti properties tht n led to effiient degrdtion of orgni moleules, inluding pollutnts, under V irrdition. Moreover, photoeletril onversion ehviour hs een reported for urnyl extended strutures 42. It is likely tht onfinement of severl urnyl moieties into well-defined, spheril strutures of nnosopi size, suh s those reported here, will ontriute to exploit these properties in tlysis nd photoeletronis 12,14. Methods Mesurements. 1 nd 13 C MR spetr were reorded on Bruker DRX-500 (500 Mz) nd AV-400 (400 Mz) spetrometers. All MR spetrl dt were nture ommunitions 3:785 DI: 10.1038/nomms1793 www.nture.om/ntureommunitions
nture ommunitions DI: 10.1038/nomms1793 ws dissolved in DMF (1 ml). Slow diffusion of etonitrile t room temperture fforded yellow rystls suitle for X-ry nlysis fter 10 dys. Log (m2/s) 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 p.p.m. Figure 6 DSY spetrum of mixture of ges 1 nd 2 in DMF d 7 t 300 K. Lignds 7 nd 8 were t 6 nd 12 mm onentrtion, respetively. DSY MR diffusion oeffiients, lulted on the sis of monodimensionl fitting nd expressed in m 2 s 1, re (from top to ottom in the spetrum): ge 2 (1.22 E-06), ge 1 (1.77 E-06), ompounds 7 nd 8 (3.10 E-06), DMF d 7 ((1.37 ± 0.02) E-05). olleted t 300 K unless otherwise speified, nd hemil shifts were reported s the delt sle in p.p.m. All R Mss spetr were reorded on Mldi TF Bruker Autoflex. DLS dt were olleted t 293 K y Mlvern nozs instrument. Singlerystl X-ry diffrtion dt were olleted on Bruker FR591 rotting node equipped with Montel mirrors with MoK α rdition (λ = 0.71073 Å) nd Bruker Apex-II Duo diffrtometer equipped with mirosoures of CuK α (λ = 1.54178 Å) nd MoK α rdition (λ = 0.71073 Å), nd ooled with n xford Cryostrem lowtemperture devie (T = 100(2) K). See Supplementry Figs S12 S16 for RTEP digrms for psules 1, 2, 1 with ylen, 11 nd 12, respetively. The Cmridge Crystllogrphi Dt Centre entries 856,283, 856,284, 856,285, 856,286 nd 856,287 ontin the supplementry rystllogrphi dt for this pper. These dt n e otined free of hrge vi www.d.m..uk/onts/retrieving.html (or from the Cmridge Crystllogrphi Dt Centre, 12 nion Rod, Cmridge CB2 1EZ, K; fx: ( + 44) 1223-336-033; or e-mil: deposit@d.m..uk; see Supplementry Dt 1 5). Synthesis of mterils. Solvents nd regents were purhsed from Shrlu Chemie SA, Pnre Quími SA, Aros rgnis, Sigm-Aldrih Co. nd Deutero Gm. All hemils were used without further purifition. Compounds 3 43, 4 44, 9 27 nd 10 28 were otined ording to literture proedures. Compound 5 ws prepred using modified literture proedure 26 in mirowve retor t 110 C for 3 h. Compound 7 ws otined y different proedure from the one reported in the literture 45. 5,11,17,23,29-Pentformyl-25,26,27,28,29-penthydroxylix[5]rene (6). In seled vil (20 ml), 25,26,27,28,29-penthydroxylix[5]rene (4) (159 mg, 0.300 mmol) nd hexmethylenetetrmine (1.60 g, 11.4 mmol) were dissolved in trifluoroeti id (12.0 ml), nd the retion mixture ws heted t 140 C for 5 h under mirowve irrdition. A volume of 35 ml of 1 M Cl nd 35 ml of CCl 3 were dded to the rude mixture, nd the two-phse system ws stirred overnight t room temperture. The queous phse ws extrted gin with CCl 3, nd the olleted orgni phses were wshed one with wter. The solvent ws evported t redued pressure, nd triturtion from dihloromethne fforded drk yellow solid (140 mg, 70%); mp: >360 C (de.); 1 -MR (400 Mz, DMS-d 6 ) δ 9.66 (s, 5, C), 7.61 (s, 10, C), 3.84 (s, 10, C 2 ); 13 C-MR (100 Mz, DMS-d 6 ) δ 190.8 (C), 161.3 (C ), 130.6 (C), 128.7 (C-C 2 ), 127.3 (C-C), 31.33 (C 2 ); RMS (m/z): [M ] lulted for C 40 29 10 669.1761; found, 669.1784 (see Supplementry Fig. S17). 25,26,27,28,29-Penthydroxylix[5]rene-5,11,17,23,29-pentroxyli id (8). To stirred mixture of pentformyllix[5]rene (6) (140 mg, 0.209 mmol) in DMS (2.6 ml) nd sodium dihydrogen phosphte (30 mg, 0.250 mmol) in 1.8 ml of wter, solution of sodium hlorite (0.264 g, 2.92 mmol) in 1.5 ml of wter ws dded dropwise t room temperture over 3 h. The retion ws stirred overnight t room temperture, nd ws then idified with onentrted Cl nd kept overnight in the refrigertor. The solid formed ws filtered, wshed with wter, then with methnol, nd dried to give pure ompound 8 s rown solid (78 mg, 50%); mp: >350 C (de.); 1 -MR (400 Mz, DMS-d 6 ): 7.66 (s, 10, C), 3.80 (s, 10, C 2 ). 13 C-MR (100 Mz, DMS-d 6 ): 167.8 (C qut ), 130.7 (C), 128.4 (C-C 2 ), 121.0 (C-C), 31.83 (C 2 ). RMS (m/z): lulted for C 40 29 15 749.1585; found, 749.1538 (see Supplementry Fig. S18). thedrl ge 1. A mixture of 7 (20 mg, 0.033 mmol), urnyl nitrte hexhydrte [ 2 ( 3 ) 2 6 2 ] (17.5 mg, 0.044 mmol) nd pyridine (11 µl, 0.133 mmol) 9.8 9.6 9.4 9.2 9.0 8.8 thedrl ge 1 with 1,4,7,10-tetrzylododene (ylen). A mixture of 7 (5.0 mg, 0.008 mmol), urnyl nitrte hexhydrte [ 2 ( 3 ) 2 6 2 ] (5.6 mg, 0.011 mmol) nd pyridine (3 µl, 0.033 mmol) ws dissolved in DMF (0.3 ml), nd ws dded to suspension of ylen (2 mg, 0.012 mmol) in 0.2 ml of DMF. The mixture ws shked for dy until omplete dissolution. Slow diffusion of etonitrile t room temperture fforded yellow rystls suitle for X-ry nlysis fter 10 dys. thedrl ge 11. A mixture of 9 (9.7 mg, 0.013 mmol) nd urnyl nitrte hexhydrte (8.6 mg, 0.017 mmol) ws dissolved in DMF-d 7 (470 µl) nd pyridined 5 (4 µl, 0.050 mmol) ws dded. After 1 week, yellow rystls suitle for X-ry nlysis were formed. thedrl ge 12. A mixture of tetr--otyllix[4]rene tetrroxyli id 10 (10 mg, 0.010 mmol), urnyl nitrte hexhydrte [ 2 ( 3 ) 2 6 2 ] (7.0 mg, 0.014 mmol) nd pyridine (4 µl, 0.042 mmol) ws dissolved in 1,1,2,2-TCE (0.4 ml), nd the mixture ws shken for 3 dys until omplete dissolution. Slow diffusion of etonitrile t room temperture fforded yellow rystls suitle for X-ry nlysis fter 10 dys. Ioshedrl ge 2. A mixture of 8 (16 mg, 0.021 mmol), urnyl nitrte hexhydrte [ 2 ( 3 ) 2 6 2 ] (15 mg, 0.038 mmol) nd pyridine (9 µl, 0.107 mmol) ws dissolved in DMF (0.7 ml). 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SA 106, 10482 10486 (2009). Aknowledgements We thnk the Ministry of Siene nd Innovtion of Spin (Grnts CTQ2008-00183 nd Consolider Ingenio 2010 CSD 2006-0003), nd the ICIQ Foundtion for finnil support. Author ontriutions S.P. nd S.S. ontriuted eqully to this work. J.M. devised the initil onept for the work, S.P. nd S.S. designed nd rried out the experiments, nd E.C.E.-A. nd M.M.-B. performed the X-ry studies nd solved the strutures. J.M. wrote the mnusript. Additionl informtion Supplementry Informtion ompnies this pper t http://www.nture.om/ ntureommunitions Competing finnil interests: The uthors delre no ompeting finnil interests. Reprints nd permission informtion is ville online t http://npg.nture.om/ reprintsndpermissions/ ow to ite this rtile: Psqule, S. et l. Gint regulr polyhedr from lixrene roxyltes nd urnyl. t. Commun. 3:785 doi: 10.1038/nomms1793 (2012). Liense: This work is liensed under Cretive Commons Attriution-onCommeril- Shre Alike 3.0 nported Liense. 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