Inorganic Chemistry Communications 11 (2008) 1113–1116

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Inorganic Chemistry Communications

journal homepage: www.elsevier .com/ locate/ inoche

Synthesis and characterization of novel supercryptands-fused porphyrazines

Ahmet Bilgin a,*, Beytullah Ertem b

a Department of Science Education, Kocaeli University, 41380 Kocaeli, Turkeyb Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey

a r t i c l e i n f o a b s t r a c t

Article history:Received 21 May 2008Accepted 18 June 2008Available online 25 June 2008

Keywords:TetraazaporphyrinPorphyrazinesCryptandsMagnesiumZinc

1387-7003/$ - see front matter � 2008 Elsevier B.V. Adoi:10.1016/j.inoche.2008.06.012

* Corresponding author. Tel.: +90 262 303 2438; faE-mail address: abilgin@kocaeli.edu.tr (A. Bilgin).

Novel metal-free (8, 9), magnesium and zinc porphyrazines (6, 7, 10, 11) containing four peripheral tetr-aza-dithiahexaoxa cyclindrical or spherical cryptand units have been prepared by tricyclotetramerizationreactions using supercryptand 4 or 5. All new products have been characterized by a combination ofmass, elemental analyses, electronic absorption, FT-IR, 1H and 13C NMR spectroscopy.

� 2008 Elsevier B.V. All rights reserved.

In the recent years, the tetraazaporphyrins have aroused re-newed research interest for a variety of reasons [1]. Unlike theirmore common tetrapyrrolic congeners, the porphyrins andphthalocyanines, they offer a much higher potential for creatingstructural diversity. With the inherent synthetic ease of includingdiverse peripheral substituents, they are seen as promising mate-rials having potential applications in diverse areas [2]. The firstsynthesis of crowns-fused porphyrazines was reported indepen-dently by the groups of Hoffman and Nolte [3,4]. The coordinationchemistry, aggregation and electrical properties of these com-pounds were investigated [5,6]. Such systems contain a metal cen-ter that is complexed by a porphyrazine ring, four macrocyclicbinding and tridentate meso-pocket sites [3–6]. That is why suchcompounds, which are exemplified by [(S2,O3 crown]4pz, shouldshow rich and varied coordination chemistry. In contrast to fusedphthalocyanine-crown ether systems, metal ion coordination bythe crown ether units in [(S2,O3 crown]4pz have profound effectson UV-vis spectra and other properties, since the key crown sulfurresidues are in direct electronic contact with the macrocyclic cen-tral chromophore [7]. In addition, the attachment of oxacrown [8],azacrown or polyaza-polythia macrocycles to porphyrazine hasreceived considerable attention since they allow for cation selec-tivity and complex stability to be enhanced through changingthe numbers and types of macrocycle donors as well as the solu-bility of porphyrazines [9–14]. Lastly, being isoelectronic in termsof p electrons with the PcH2 skeleton, these types of polynucleat-ing macrocyclic compounds are promising new materials withpotential applications in different fields such as electron transfer

ll rights reserved.

x: +90 262 303 2403.

[15], magnetic interactions [16], optical phenomena [17], ex-cited-state reactivity [18], mixed valency [19], and ionophoricactivity [20].

Since the first cyclindrical [21,22] or spherical [23] macrotricylicligands were reported by Lehn and co-workers, hundreds of macro-polycyclic compounds with unusual shapes have been preparedand their properties have been investigated [24–26]. A very activecurrent research activity in this area has led to the developmentof numerous procedures for effecting macrocyclization such astemplate effects and high dilution techniques, thus giving accessto a great number of new macrocycles. Owing to their architecturaland functional plasticity, supercryptand compounds are especiallyattractive for designing both biomimetic and abiotic receptor mol-ecules for inorganic and organic substrates [27,28]. In addition,macropolycylic species continue to be an active field of researchdue to their use as models for metalprotein [29] and respiratorypigments [30].

Our previous papers have described a series of phthalocyanineswith various functional groups. These phthalocyanines have N-, O-and S-containing functionalities such as diazadioxa [31], cryptand[26,32], crown ether fused diloop [33], diazadithia macrocyclicwith tert-butyl [34], and tetrathiamonoaza macrocyclic [35]. Theimmediate consequences of these peripheral substituents are en-hanced solubility in common organic solvents and additional do-nor sites for alkali or transition metal ions.

In this communication, the first examples of novel porphyra-zines are reported, in which four peripheral supercryptands arebound (Scheme 1). Specifically, the magnesium and metal-free moi-eties of the porphyrazines substituted cyclindrical or sphericalcryptands were synthesized starting from 5,8-dithiadodec-6-en-6,7-dicarbonitrile-1,2-di-p-toluenesulfonate 1 [36] including more

NC

NC

N

O

O

N

N

O

O

N

O

O

S

S

CN

CN

S

SO

O

Ts

Ts

1

O

N

O

N

O

N

O

N

O

O

H

H

2

4

Na2CO3

CH3CN90 ˚CN2(g)47%

Na2CO3

CH3CH2CN120 ˚CN2(g)24%

OO

O

N

N

O

N

O

N

OCN

CN

S

S

5

OO

O

N

N

O

N

O

N

O

H

H

3

Mg(OBu)2

BuOH

N2(g)

125 ˚C15%

Mg(OBu)2

BuOH

N2(g)

125 ˚C21%

O

O

ON

N

O

N

O

N

O

S

S

OOO

N

N

ON

O

N

O

S

S

O

O

ON

N

O

N

O

N

O

S

S

OO O

N

N

ON

O

N

O

S

S

N

N

N

N

N

N

N

N

Mg

6 7

CF3COOH25 ˚C

N2(g)

67%

CF3COOH25 ˚C

N2(g)

75%

H2Pz H2Pz'8 9

N

O

O

N

N

O

O

N

O

O

S

S

N

O

O

N

N

O

O

N

O

O

S

S

N O

O N

N O

O N

O

O

S

S

N

N

N

N

N

N

N

N

Mg

NO

ON

NO

ON

O

O

S

S

DMF/PhCl110 ˚C

N2(g)

79%

Zn(OAc)2

10ZnPz

DMF/PhCl110 ˚C

N2(g)

79%

Zn(OAc)2

11ZnPz'

Scheme 1. Synthesis of novel porphyrazines (6–9).

1114 A. Bilgin, B. Ertem / Inorganic Chemistry Communications 11 (2008) 1113–1116

reactive ditosylate groups because of producing better yields incomparison to analogous dichloro systems for the synthesis of sat-urated polyazamacrocycles [37]. Reaction of the latter compoundwith 4,40-[ethane-1,2-diyl-bis(oxyethane-2,1-diyl)]bis-1,7-dioxa-4,10-diazacyclododecane 2 [38] or 4,10,16,22,27,30-hexaoxa-1,7,13,19-tetrazabicyclo [11.11.8] dotriacontane 3 [39] in acetonitrileor propionitrile, in the presence of sodium carbonate, yieldedsupercryptands 4 [40] and 5 [40] (Scheme 1). The template effectof sodium cations and the effect of ditosylates account for thehigh yield obtained in the desired ring closure. Products 4 (47%)and 5 (24%) were isolated after purification by column chromatog-raphy on silica gel [eluent, CHCl3–MeOH–NH4OH, 98:1.5:0.5] or[eluent, CHCl3–MeOH–NH4OH, 98:1:1] (M.p. 218–219, 211–212 �C, respectively). The elemental analyses and ES mass spectrumdata for 4 and 5 were satisfactory: 684.42 [M]+ and 684.64 [M]+,respectively.

The porphyrazines substituted supercryptands were preparedby the Mg(II) template cyclization of the appropriate supercrypt-and (4 or 5) as described (Scheme 1) [41]. The products were puri-fied by column chromatography on silica gel. The cylindricalcryptand derivative MgPz 6 [42] and spherical cryptand derivativeMgPz 7 [42] were obtained in 15% or in 21% yields, respectively, allas dark blue powders. MgPz 6 and MgPz 7 were finally demetalatedwith trifluoroacetic acid to give the metal-free derivatives H2Pz 8[43] in 67% yield and H2Pz0 9 [43] in 71% yield as dark blue to pur-ple powders. In the 1H NMR spectra of 8 and 9, the typical shieldingof inner core protons was seen as broad signals at d = �1.70 (8) and�1.45 ppm (9), which could be attributed to the NH resonances asconfirmed by deuterium exchange. The elemental analyses and ESmass spectrum data of all the porphyrazines (6–9) were satisfac-tory. The molecular ion peaks at m/z = 2761.53 [M]+ 6, 2761.42[M]+ 7, 2739.52 [M]+ 8 (see Fig. 1) and 2739.54 [M]+ 9 were found

Fig. 1. Mass spectrum of 8.

300 400 500 600 700 800 900

0

1

2

3

Wavelength, λ (nm)

Abs

orba

nce

(a.u

.)

Fig. 2. Electronic absorption spectra of 6 (������) (1.50 � 10�5 M), 7 (- - - -)(1.35 � 10�5 M), 8 (—) (1.60 � 10�5 M) and 9 ( ) (1.40 � 10�5 M) in CHCl3.

A. Bilgin, B. Ertem / Inorganic Chemistry Communications 11 (2008) 1113–1116 1115

by the ES/MS technique for porphyrazines together with some rea-sonable ion fragments.

Porphyrazinato zinc(II) 10 [44] and 11 [44] were prepared fromcompound 8 or 9, Zn(OAc)2 and a mixture of DMF (4 mL) and PhCl(8 mL) under N2 gas atmosphere in 79% or in 83% yields, respec-tively. The dark blue powders 10 and 11 were isolated followingchromatography. In the case of compounds 10 and 11, N�H bondsin porphyrazine core of compound 8 at 3280 cm�1 and 9 at3265 cm�1 were vanished in the IR spectra. Other IR vibrations of10 and 11 are so familiar with compound 8 or 9 except littlechanges. The 1H NMR spectra of these compounds (10,11) were al-most identical with those of the metal-free porphyrazines (8,9),with the absence of the N�H protons belonging to the cavity ofthe porphyrazine core. Also, it should be mentioned that the peaksof the 1H NMR spectra are broad as encountered in some other sol-uble porphyrazines. The molecular ion peaks at m/z = 2806.34[M + H]+ 10 and 2806.46 [M + H]+ 11 were found by the LC/ES+

technique for porphyrazines together with some reasonable ionfragments. The results of elemental analysis and the mass spectraldata for the zinc(II) porphyrazines 10 and 11 confirmed that the ra-tio of reactants was 1:1 metal:ligand.

Fig. 2 shows electronic absorption spectra of metal-free andmagnesium porphyrazines (6–9) in chloroform solutions. The mag-nesium MgPz (6, 7) and zinc compounds ZnPz (10, 11) exhibit sin-gle Q-band maximum at around 680 nm, whereas the metal-freeH2Pz 8 and H2Pz0 9 display two broad bands with maxima ataround 715 and 645 nm caused by a p ? p* transition. A second in-tense and broad p ? p* transition in the range 300–400 nm, whichis called Sored or B-band, is also a characteristic of porphyrazinederivatives (see Fig. 2). In addition, the broad band around510 nm which is observed for the metalated as well as for the me-tal-free porphyrazines, has been attributed to an n ? p* transitionthat involves the peripheral S atoms [45]. All novel porphyrazinederivatives that were synthesized under the framework of this

manuscript were titrated against various heavy metal cations(Ag+, Hg2+, Cd2+ and Pb2+), alkali and alkaline earth metal cations(Li +, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+ and Ba2+), but there was no obser-vable changes in the UV–vis spectra. This is probably due to thesteric hindrance of the bulky peripheral groups of the porphyra-zines which prevent an effective p ? p* interaction between theporphyrazine subunits. On the other hand, it can be expected thatheavy metal cations might be bound (coordinated) to soft sulphuratoms, but nevertheless these sulphur atoms are very far awayfrom the central cryptand cavity. Further, there is no significantchanges regarding n ? p* interactions, and is proved that heavymetal ions do not coordinate with soft sulphur atoms located incentral cryptand cavities.

In conclusion, the first examples of novel supercryptands-fusedporphyrazines were synthesized. All new compounds were charac-terized by elemental analysis and spectral methods; in all cases thespectroscopic data were consistent with the assigned structures.

Acknowledgment

This work was supported by The Scientific and Technical Re-search Council of Turkey (TUBITAK), Project Number: TBAG-2453(104T065) (Ankara, Turkey).

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(1995) 931.[39] K.E. Krakowiak, J.S. Bradshaw, J. Org. Chem. 69 (1995) 7070.[40] General procedure for the synthesis of supercryptands 4 or 5: A mixture of

compounds 2 or 3 (4.63 g, 10 mmol) and anhydrous Na2CO3 (10.6 g,100 mmol) in dry acetonitrile or propionitrile (300 ml) was stirred at 45 �Cunder nitrogen for 45 min. Compound 1 (6.04 g, 10.67 mmol) was slowlyadded to this mixture and the reaction mixture was heated at 90 or 120 �C for6 days. At the end of this period, the mixture was cooled to room temperatureand filtered using Celite as the filtering agent and washed withdichloromethane (75 ml). The major liquor and washing solvents werecombined and evaporated to dryness under reduced pressure. The residuewas purified by column chromatography on silica gel [CHCl3–MeOH–NH4OH,98:1.5:0.5] or [CHCl3–MeOH–NH4OH, 98:1:1] as eluents. The appropriatefraction was evaporated, 50 ml of dichloromethane was added, and themixture was filtered off and evaporated to give supercryptands 4 (47%) and 5

(24%). Compound 4: Anal. Calcd. for C32H56N6O6S2: C, 56.11; H, 8.24; N, 12.27;S, 9.36. Found: C, 56.48; H, 8.57; N, 12.09; S, 9.64%. IR (KBr disc, cm�1): 2210(C§N). 1 H NMR (CDCl3, 300 MHz): d = 3.64 (m, 24H), 3.32 (m, 20H), 3.21 (t,4H), 3.02 (t, 4H), 1.92 (br m, 4H); 13C NMR (CDCl3, 75 MHz): d = 123.3, 112.3,70.6–69.4, 56.1, 55.3, 54.8, 48.7, 34.5, 28.3. Compound 5: Anal. Calcd. forC32H56N6O6S2: C, 56.11; H, 8.24; N, 12.27; S, 9.36. Found: C, 56.32; H, 8.41; N,12.54; S, 9.53%. IR (KBr disc, cm�1): 2212(C§N). 1H NMR (CDCl3, 300 MHz):d = 3.72 (m, 24H), 3.29 (m, 20H), 3.16 (t, 4H), 3.08 (t, 4H), 2.01 (br m, 4H). 13CNMR (CDCl3, 75 MHz): d = 122.4, 110.9, 71.2–69.9, 55.9, 54.4, 50.7, 49.2, 32.9,29.1.

[41] C.J. Schramm, B.M. Hoffman, Inorg. Chem. 19 (1980) 383.[42] General procedure for the synthesis of magnesium porphyrazines 6 or 7: a

mixture of 1-butanol (3 mL), Mg (2.4 mg, 1 mmol), and I2 (one small crystal)was heated to reflux for 24 h under N2. The suspension was cooled, anddinitriles 4 or 5 (1.71 g, 2.5 mmol) in 1-butanol (50 mL) were added dropwiseand the mixture was further heated at reflux for 6 h. The deep blue suspensionwas allowed to cool, filtered (silica) and the solids washed with MeOH. Rotaryevaporation and chromatography (silica, EtOAc–MeOH, 98:2) or (silica, EtOAc–MeOH, 96:4) gave Mg–porphyrazines 6 (15%) and 7 (21%) as dark blue solids.Compound 6: M.p. >310 �C. Anal. Calcd. for C128H224N24O24S8Mg: C, 55.62; H,8.17; N, 12.16; S, 9.28; Mg, 0.88. Found: C, 55.93; H, 8.39; N, 11.95; S, 9.47; Mg,0.71%. IR (KBr disc, cm-1): 1645(C@N). 1H NMR (CDCl3, 300 MHz): d = 3.61 (m,96H), 3.34 (m, 80H), 3.23 (t, 16H), 3.06 (t, 16H), 1.89 (br m, 16H). 13C NMR(CDCl3, 75 MHz): d = 156.2, 135.8, 70.4–69.3, 55.8, 55.4, 54.6, 49.2, 35.1, 29.4.UV/vis (CHCl3): kmax (loge) = 683 (5.21), 624 (4.65), 510 (4.67), 320 (5.28).Compound 7: M.p. >310 �C. Anal. Calcd. for C128H224N24O24S8Mg: C, 55.62; H,8.17; N, 12.16; S, 9.28; Mg, 0.88. Found: C, 55.44; H, 8.37; N, 12.43; S, 9.56; Mg,0.67%. IR (KBr disc, cm�1): 1647(C@N). 1H NMR (CDCl3, 300 MHz): d = 3.69 (m,96 H), 3.31 (m, 80H), 3.19 (t, 16H), 3.04 (t, 16H), 1.98 (br, m, 16H). 13C NMR(CDCl3, 75 MHz): d = 155.6, 136.6, 71.3–69.1, 56.0, 54.6, 50.9, 48.9, 33.3, 29.3.UV/vis(CHCl3): kmax (loge) = 678 (5.28), 636 (4.86), 508 (4.52), 329 (5.34).

[43] General procedure for the synthesis of metal-free porphyrazines 8 or 9: In the, amixture of trifluoroacetic acid (1 mL) and porphyrazines 7 or 8 (56 mg,0.02 mmol) were stirred at 25 �C for 20 h, poured onto ice and water (15 mL)and the resulting suspension was brought to pH 7 with ammonia (32%). Theprecipitate was collected via vacuum filtration, washed with water, acetoneand chromatographed (silica, CHCl3–MeOH–NH4OH, 97:2.5:0.5 or silica,CHCl3–MeOH–NH4OH, 98:1.75:0.25) to yield metal-free porphyrazines 8(67%) or 9 (75%). Compound 8: M.p. >310 �C. Anal. Calcd. for C128H226-N24O24S8: C, 56.07; H, 8.31; N, 12.26; S, 9.35. Found: C, 56.28; H, 8.06; N, 12.49;S, 9.67%. IR (KBr disc, cm�1): 3280 (N–H). 1 H NMR (CDCl3, 300 MHz): d = 3.59(m, 96H), 3.37 (m, 80H), 3.25 (t, 16H), 3.01 (t, 16H), 1.92 (br m, 16H), �1.70 (brs, 2H, NH). 13C NMR (CDCl3, 75 MHz): d = 152.9, 134.3, 70.1–69.2, 55.9, 54.7,54.3, 49.4, 34.7, 28.9. UV/vis (CHCl3): kmax (loge) = 718 (5.08), 639 (4.94), 512(4.80), 360 (5.21), 339 (5.19). Compound 9: M.p. >310 �C. Anal. Calcd. forC128H226N24O24S8: C, 56.07; H, 8.31; N, 12.26; S, 9.35. Found: C, 56.28; H, 8.06;N, 12.49; S, 9.67%. IR (KBr disc, cm�1): 3265 (N–H). 1H NMR (CDCl3, 300 MHz):d = 3.67 (m, 96H), 3.40 (m, 80H), 3.20 (t, 16H), 3.06 (t, 16H), 1.96 (br m, 16H),�1.45 (br, s, 2H, NH). 13C NMR (CDCl3, 75 MHz): d = 153.4, 136.7, 70.9–69.4,56.4, 53.8, 52.7, 48.6, 34.2, 29.1. UV/vis (CHCl3): kmax (loge) = 716 (5.18), 648(4.97), 510 (4.84), 349 (5.27).

[44] General procedure for the synthesis of zinc porphyrazines 10 or 11: A 25 mLSchlenk tube was charged with the porphyrazine 8 or 9 (137 mg, 0.05 mmol),Zn(OAc)2 (92 mg, 0.5 mmol) in a mixture of DMF (4 mL) and PhCl (8 mL) andthen evacuated, refilled three times with nitrogen, and connected to a vacuumline. The mixture was heated to 110 �C under a N2 gas and stirred for 24 h. Thesolvent was then removed by vacuum distillation, and the solid residue waswashed with 1% HCl/MeOH and filtered. The resultant solid was washed withH2O, MeOH and Me2CO and chromatographed (silica, CHCl3–Me2CO, 98:2 orsilica, EtOAc–MeOH–NH4OH, 97:2.5:0.5) to afford zinc porphyrazines 10 (79%)or 11 (83%) as dark blue solids. Compound 10: M.p. >310 �C. Anal. Calcd. forC128H224N24O24S8Zn: C, 54.81; H, 8.05; N, 11.98; S, 9.14; Zn, 2.33. Found: C,54.65; H, 8.27; N, 12.21; S, 9.41; Zn, 2.64%. IR (KBr disc, cm�1): 1642(C@N). 1 HNMR (CDCl3, 300 MHz): d = 3.64 (m, 96H), 3.32 (m, 80H), 3.26 (t, 16H), 3.02 (t,16H), 1.91 (br m, 16H). 13C NMR (CDCl3, 75 MHz): d = 155.9, 135.5, 70.3–69.5,55.7, 55.5, 54.9, 49.2, 34.7, 29.1. UV/vis (CHCl3): kmax (loge) = 679 (5.12), 620(4.43), 508 (4.61), 325 (5.31). Compound 7: M.p. >310 �C. Anal. Calcd. forC128H224N24O24S8Zn: C, 54.81; H, 8.05; N, 11.98; S, 9.14; Zn, 2.33. Found: C,55.06; H, 8.28; N, 11.67; S, 9.23; Zn, 2.54%. IR (KBr disc, cm�1): 1640(C = N). 1HNMR (CDCl3, 300 MHz): d = 3.71 (m, 96H), 3.29 (m, 80H), 3.23 (t, 16H), 3.10 (t,16H), 1.92 (br, m, 16H). 13C NMR (CDCl3, 75 MHz): d = 155.7, 136.9, 71.0–69.3,55.8, 54.1, 50.4, 49.1, 34.6, 28.7. UV/vis(CHCl3): kmax (loge) = 674 (5.20), 632(4.72), 510 (4.43), 320 (5.40).

[45] P. Doppelt, S. Huille, New J. Chem. 14 (1990) 607.