10740 Chem. Commun., 2011, 47, 10740–10742 This journal is c The Royal Society of Chemistry 2011

Cite this: Chem. Commun., 2011, 47, 10740–10742

Weak Ag� � �Ag and Ag� � �p interactions in templating

regioselective single and double [2+2] reactions of

N,N0-bis(3-(4-pyridyl)acryloyl)–hydrazine: synthesis of anunprecedented tricyclohexadecane ring systemw

Ramkinkar Santra, Kaustuv Banerjee and Kumar Biradha*

Received 4th July 2011, Accepted 9th August 2011

DOI: 10.1039/c1cc13994k

Synthesis of a stereospecific four–twelve–four fused tricyclic

compound containing a tetraamide macrocycle has been achieved

by the solid state [2+2] reaction through utilization of Ag� � �Aginteraction. The influence of anions on crystal packing has been

utilized for the synthesis of a regioselective mono cyclobutane

compound via the Ag� � �p interactions.

The utilization of supramolecular chemistry for the stereo and

regio chemically controlled covalent synthesis has been

gaining significant attention in recent days.1–4 In particular

hydrogen bonding or coordination bonding driven solid state

[2+2] reactions have been successfully employed for the

synthesis of cyclobutane,5 cyclophane,6 ladderane7 and tricyclo

decane derivatives.8 However, finding a template which is

suitable for a given class of wide variety of olefins is still a

challenge due to the newer sterical demands and interfering

interaction forces exerted by the substituents. Moreover the

template tolerance to the wide variety of functionality is not

explored.9 We have recently shown that the photodimerization

of a cross-conjugated diene, intervened by a keto functionality,

resulted in a four–six–four fused tricyclo decane derivative

utilizing a hydrogen bonding template.8 Interestingly, it was

also shown by us that the double [2+2] reactions proceed in a

stepwise manner, that is they do not react simultaneously but

one after the other. In order to increase the scope of findings

about the mechanism as well as the synthesis of higher tricyclo

ring systems containing multiple functional groups, we have

considered a longer molecule containing versatile hydrogen

bonding functional groups, such as N,N0-bis(3-(4-pyridyl)acryloyl)-

hydrazine (4-PAH). The double [2+2] photochemical reaction

of this molecule is expected to result in a four–twelve–four

fused tricyclohexadecane (TCHD) ring system. We note here

that to date no such molecules containing four–twelve–four

fused rings are reported in the literature.10 The tricyclo

derivatives containing four pyridyl units are effective building

blocks for the construction of MOF materials.11 In this

communication we report successful templation of 4-PAH

by Ag� � �Ag and Ag� � �p interactions that leads to the

regioselective formation of TCHD and a mono cyclobutane

product (MCB), respectively, depending on the presence of anions.

Compound 4-PAH was synthesized by the reaction of

hydrazine with the pentafluorophenyl ester of 4-pyridyl acrylic

acid in dry DMF. Light yellow coloured crystals of 4-PAH�4H2O were grown by crystallizing from DMF. Crystal struc-

ture analysis reveals that the molecule has the planar geometry

with the anti orientation of amide groups (Fig. S1, ESIw). Themolecules assemble into a 2D-herringbone type layer via the

N–H� � �N(Py) hydrogen bonding and contain the cavities of

dimension 10.2 � 11.6 A, which are occupied by water

molecules. These layers exhibit ‘AAA’ type packing in the

crystal lattice such that the double bonds from the adjacent

layers have parallel orientation, with the centroid to centroid

distance of 3.765 A. However, the 4-PAH was found to be

photostable despite irradiating for longer times. The observed

unreactivity could be due to the high displacement parameter

d1 (Table S1, ESIw) which is as high as 1.8 A.12

Given the potential hydrogen bonding donors on 4-PAH,

the organic hydrogen bonding templates such as resorcinol,

phloroglucinol and 5-methoxy resorcinol are found to be

ineffective in driving the co-crystal formation by conventional

solvent evaporation methods. Even the mechanically co-grinded

materials of 4-PAH with any of the above templates exhibited

neither complex formation nor photochemical reactivity.

Recently we have shown that argentophilic interactions are better

templates even in the presence of strong hydrogen bonding

functional groups such as –COOH and –CONH2 groups.13,14

These groups were found to show no interference in Ag(I)

coordination to pyridine and also in interaction of anions with

Ag(I). Therefore it was thought that the photochemical reactions

of 4-PAH may be promoted through the synthesis of silver

coordination polymers. Further, to explore the influence of

Department of Chemistry, Indian Institute of Technology,Kharagpur-721302, India. E-mail: kbiradha@chem.iitkgp.ernet.in;Fax: +91-3222-282252; Tel: +91-3222-283346w Electronic supplementary information (ESI) available: Experimentaldetails and characterization of the compounds by NMR and IRspectra, powder XRD patterns; a table for geometrical parametersof aligned double bond pairs; figures for 1H NMR spectra recorded atvarious stages of irradiation; crystallographic information of thecompounds explained in detail. CCDC 826880–826884. For ESI andcrystallographic data in CIF or other electronic format see DOI:10.1039/c1cc13994k

ChemComm Dynamic Article Links

www.rsc.org/chemcomm COMMUNICATION

Dow

nloa

ded

by U

nive

rsity

of

Mis

sour

i at C

olum

bia

on 2

1 M

arch

201

3Pu

blis

hed

on 2

2 A

ugus

t 201

1 on

http

://pu

bs.r

sc.o

rg |

doi:1

0.10

39/C

1CC

1399

4KView Article Online / Journal Homepage / Table of Contents for this issue

This journal is c The Royal Society of Chemistry 2011 Chem. Commun., 2011, 47, 10740–10742 10741

anions on the photochemical reactivity of 4-PAH, we have

studied the complexation reactions of 4-PAH with AgNO3 and

AgClO4.

The direct mixing of methanolic solutions of 4-PAH and silver

perchlorate or nitrate produced orange coloured precipitates

which were found to be photochemically unreactive. The

mechanochemical grinding of 4-PAH and silver salts was also

found to produce similar orange coloured materials which

were also found to be photostable. However, we are successful

in obtaining light yellow coloured crystals of complex

[Ag(4-PAH)(ClO4)]n, 1, by layering methanolic solution of

silver perchlorate over the MeOH–DCM (in 1 : 2 ratio) solution

of 4-PAH. The bulk purity of the complex 1 was confirmed by

the XRPD patterns and elemental analysis (see ESIw).Interestingly, crystals of 1 were found to be photoreactive

and 1H NMR spectra of complex 1 after irradiating for seven

hours clearly showed the formation of the anticipated TCHD

compound in B100% yield.

The crystal structurez of complex 1 is analyzed in order to

understand the observed reactivity. In 1, the asymmetric unit is

constituted by two units each of Ag(I), perchlorate and

4-PAH. The Ag(I) atoms exhibit linear coordination geometry

and join the units of 4-PAH into a one-dimensional network.

The Ag� � �Ag interactions (3.399 and 3.477 A) link two of these

chains to form a double chain in which both the double bonds

of 4-PAH contain reactive arrangement (Table S1, ESIw) toform the TCHD molecule (Fig. 1a). Ag� � �Ag interaction is

assisted by the unsymmetrical bridging of Ag atoms by ClO4�

anions. Further, the double chains are packed to form a layer

in which p� � �p stacking (between the bis-amide moiety and the

pyridyl ring) and weak Ag� � �p (olefin) interactions play a

significant role (Fig. 1b). Such a type of arrangement resulted

in the possibility for the formation of the MCB product due to

the single [2+2] reaction, the alignment parameters are similar

to those of the double [2+2] reaction. However, 1 exclusively

forms the double [2+2] reaction product TCHD in 100%

yield. The preference for double [2+2] reaction may be

justified by the stronger interactions involved within the

double chain compared to those between the double chains.

Repeating the reaction with AgNO3 in place of AgClO4

resulted in the single crystals of [Ag(4-PAH)(NO3)]n, 2. The crystal

structure analysis of 2 reveals that the asymmetric unit,

unlike in 1, is constituted by one unit each of Ag(I), NO3 and

4-PAH. However, it also forms a similar double chain via

Ag� � �Ag interactions which are bridged by NO3� anions in

unsymmetrical fashion (Fig. 2a). In this structure, the displacement

value of d1 (Table S1, ESIw) for double [2+2] reaction, within

the double chain, was found to be much higher (2.302 A) than

that of single [2+2] reaction (0.891 A) between the double

chains. Further, the interactions between the ligands within

the double chain are found to be weaker compared to 1. In

particular, the electrostatic interactions between the N–H and

CQO groups were found to be longer in 2 compared to 1

(HN� � �CO: 3.755 A in 2 vs. 3.533 and 3.571 A in 1). In

addition, the Ag� � �p interactions between the double chains

in 2 were found to be shorter than those of 1 (3.435 A in 2 vs.

3.791 and 4.423 A in 1) (Fig. 2b). Due to the smaller d1 value

for single [2+2], stronger interactions between the double

chains and weaker interactions within the double chain, the

irradiation of 2 led to the exclusive single [2+2] reaction

between the adjacent double chains to give the product

MCB. We note here that the small differences in the packing,

due to the adjustments of different shapes and size of the

anions, resulted in the regioselective photochemical reactions

of 4-PAH.

In order to get some insight into the reaction mechanism of

double [2+2] reaction, 1H NMR spectra of complex 1 were

recorded at various stages of irradiation (Fig. S3, ESIw). The1H NMR spectra of partially irradiated material indicate

several new peaks corresponding to the mono-cyclo butane

intermediate. One new peak in the cyclobutane region (as the

other merges with that of TCHD) and two new peaks for NH

protons of the intermediate were clearly observed. These

studies clearly indicate that the double [2+2] reaction is

proceeding through the stepwise mechanism and therefore

through the formation of the corresponding mono-cyclo butane

intermediate.

Finally, the tricyclohexadecane compound, TCHD, and

MCB that are synthesized from complexes 1 and 2, respectively,

were isolated in pure form by acid–base work-up. Crystals

suitable for single crystal X-ray diffraction study were grown

by recrystallizing TCHD and MCB from DMSO and

Fig. 1 Illustrations for crystal structure of complex 1: (a) space filling

view of the double chain; (b) layer formed by the packing of double

chains: Ag� � �Ag, anion bridging, NH� � �CO and Ag� � �p interactions

are shown by coloured dotted lines, the alignments of double bonds

are shown by coloured ellipses.

Fig. 2 Illustrations for crystal structure of complex 2: (a) space filling

view of double chain, compare with Fig. 1a; (b) layer formed by the

packing of double chains: Ag� � �Ag, anion bridging, NH� � �CO, Ag� � �pand p� � �p interactions are shown by coloured dotted lines, the

alignments of double bonds are shown by coloured ellipses.

Dow

nloa

ded

by U

nive

rsity

of

Mis

sour

i at C

olum

bia

on 2

1 M

arch

201

3Pu

blis

hed

on 2

2 A

ugus

t 201

1 on

http

://pu

bs.r

sc.o

rg |

doi:1

0.10

39/C

1CC

1399

4K

View Article Online

10742 Chem. Commun., 2011, 47, 10740–10742 This journal is c The Royal Society of Chemistry 2011

MeOH–H2O mixture respectively. The crystal structure of

TCHD exhibits significant differences compared to that of

the supramolecular dimer observed in 1 (Fig. 3a). The flexibility

of the central ring allows some geometry adjustments: the

amide groups in TCHD have all cis geometry, the CQO and

the N–N bonds are in the transoid orientation and the

HN–NH groups have the torsion of 108.221. Further the

dimer sits on the crystallographic centre of symmetry. Geometry

of the MCB on the other hand is comparable to that of the

supramolecular dimer observed in 2 (Fig. 3b). The dimer MCB

was found to contain the centre of symmetry. Here the

interplanar angle between the two amide planes is about

26.551. The ethylenic bond is planar to the adjacent amide

but makes an angle of 17.351 with the pyridyl ring.

In summery, our results demonstrate an efficient approach for

the synthesis of a tetrapyridyl tricyclic (four–twelve–four fused)

compound having a core tetra-amide macrocycle by utilizing

Ag� � �Ag interactions. Here, we have shown for the first time that

the counterion effect in Ag(I) complexes can alter the regioselectivity

of solid state [2+2] reaction in dienes. The results reported

here enhance the scope of solid-state [2+2] reactions for the

synthesis of a wide variety of complex molecules.

We acknowledge DST, New Delhi, India, for financial

support, DST-FIST for the single crystal X-ray diffractometer

and R. Santra and K. Banerjee wish to acknowledge UGC and

CSIR, respectively, for research fellowships.

Notes and references

z Crystal data for (4-PAH4H2O): C16H22N4O6, M = 366.38, mono-clinic, P21/n, a = 3.7791(7) A, b= 12.616(2) A, c = 17.874(3) A, b =95.028(6)1, V = 848.9(3) A3, Z = 2, Dcal = 1.433 Mg m�3, 1058reflections out of 1499 unique reflections with I 4 2s(I), 1.981 o y o24.991, final R-factors R1 = 0.0465, wR2 = 0.1265. Crystal data for 1:C16H14AgClN4O6, M = 501.63, triclinic, P%1, a = 7.5856(12) A,b = 14.516(2) A, c = 17.684(3) A, a = 71.470(5)1, b = 80.448(5)1,g = 77.098(5)1, V= 1790.1(5) A3, Z= 4, Dcal = 1.861 Mg m�3, 2659reflections out of 6240 unique reflections with I4 2s(I), 1.221o yo 251,final R-factors R1 = 0.0652, wR2 = 0.1374. Crystal data for 2:C16H14AgN5O5, M = 464.19, triclinic, P%1, a = 8.224(3) A,b = 8.903(3) A, c = 12.642(4) A, a = 86.630(11)1, b = 80.050(10)1,

g = 66.214(9)1, V = 834.2(5) A3, Z = 2, Dcal = 1.848 Mg m�3, 1808reflections out of 2879 unique reflections with I 4 2s(I), 1.641 o y o251, final R-factors R1 = 0.0636, wR2 = 0.1554. Crystal data for(TCHD6H2O): C32H40N8O10, M = 696.72, monoclinic, C2/c,a = 17.253(6) A, b = 12.694(5) A, c = 17.639(7) A, b =116.174(11)1, V = 3467(2) A3, Z = 4, Dcal = 1.335 Mg m�3, 1839reflections out of 3057 unique reflections with I 4 2s(I), 2.071 o y o24.991, final R-factors R1 = 0.0714, wR2 = 0.1857. Crystal data for(MCB4H2O): C32H36N8O8, M = 660.69, triclinic, P%1, a = 4.7469(9)A, b=9.6101(18) A, c=17.895(3) A, a=84.941(6)1, b=84.373(8)1,g = 80.613(6)1, V = 799.4(3) A3, Z = 1, Dcal = 1.372 Mg m�3, 1834reflections out of 2625 unique reflections with I 4 2s(I), 1.151 o y o251, final R-factors R1 = 0.0668, wR2 = 0.1796.

1 (a) G. M. J. Schmidt, Pure Appl. Chem., 1971, 27, 647–678;(b) V. Ramamurthy and K. Venkatesan, Chem. Rev., 1987, 87,433–481; (c) F. Toda, Organic Solid-State Reactions, KluwerAcademic Publishers, Dordrecht, 2002; (d) J. W. Lauher,F. W. Fowler and N. S. Goroff, Acc. Chem. Res., 2008, 41,1215–1229.

2 (a) M. Yoshizawa, J. K. Klosterman andM. Fujita, Angew. Chem.,Int. Ed., 2009, 48, 3418–3438; (b) M. D. Pluth, R. G. Bergman andK. N. Raymond, Acc. Chem. Res., 2009, 42, 1650–1659.

3 (a) R. J. Hooley and J. J. Rebek, Org. Biomol. Chem., 2007, 5,3631–3636; (b) C. D. Meyer, C. S. Joiner and J. F. Stoddart, Chem.Soc. Rev., 2007, 36, 1705–1723.

4 (a) B. Moulton and M. J. Zaworotko, Chem. Rev., 2001, 101,1629–1658; (b) G. R. Desiraju, Angew. Chem., Int. Ed., 2007, 46,8342–8356; (c) D. Braga and F. Grepioni, Making Crystals byDesign: Methods, Techniques and Applications, Wiley-VCH,Weinheim, 2007.

5 (a) R. C. Grove, S. H. Malehorn, M. E. Breen and K. A. Wheeler,Chem. Commun., 2010, 46, 7322–7324; (b) W.-Z. Zhang,Y.-F. Han, Y.-J. Lin and G.-X. Jin, Organometallics, 2010, 29,2842–2849; (c) G. K. Kole, G. K. Tan and J. J. Vittal, Org. Lett.,2010, 12, 128–131; (d) S. Dutta, D.-K. Bucar andL. R. MacGillivray, Org. Lett., 2011, 13, 2260–2262.

6 (a) T. Friscic and L. R. MacGillivray, Chem. Commun., 2003,1306–1307; (b) D. Liu, Z.-G. Ren, H.-X. Li, J.-P. Lang, N.-Y. Liand B. F. Abrahams, Angew. Chem., Int. Ed., 2010, 49, 4767–4770;(c) S.-Y. Yang, P. Naumov and S. Fukuzumi, J. Am. Chem. Soc.,2009, 131, 7247–7249.

7 X. Gao, T. Friscic and L. R. MacGillivray, Angew. Chem., Int. Ed.,2004, 43, 232–236.

8 (a) R. Santra and K. Biradha, CrystEngComm, 2008, 10,1524–1526; (b) R. Santra and K. Biradha, CrystEngComm, 2011,13, 3246–3257.

9 (a) B. R. Bhogala, B. Captain, A. Parthasarathy andV. Ramamurthy, J. Am. Chem. Soc., 2010, 132, 13434–13442;(b) M. Linares and A. Briceno, New J. Chem., 2010, 34, 587–590.

10 A search in SciFinder for four–twelve–four fused ring systems withany type of atoms and bonds resulted only in two compounds (seeESIw).

11 (a) D. J. Tranchemontagne, Z. Ni, M. O’Keeffe and O. M. Yaghi,Angew. Chem., Int. Ed., 2008, 47, 5136–5147; (b) S. Bureekaew,H. Sato, R. Matsuda, Y. Kubota, R. Hirose, J. Kim, K. Kato,M. Takata and S. Kitagawa, Angew. Chem., Int. Ed., 2010, 49,7660–7664; (c) K. Biradha, M. Sarkar and L. Rajput, Chem.Commun., 2006, 4169–4179; (d) G. S. Papaefstathiou andL. R. MacGillivray, Angew. Chem., Int. Ed., 2002, 41,2070–2073; (e) A. M. P. Peedikakkal, C. S. Y. Peh, L. L. Kohand J. J. Vittal, Inorg. Chem., 2010, 49, 6775–6777.

12 For the exact definitions and importance of the parameters d, d1,d2, y, y1 and y2 see: K. Gnanaguru, N. Ramasubbu, K. Venkatesanand V. Ramamurthy, J. Org. Chem., 1985, 50, 2337–2346.

13 R. Santra and K. Biradha, Cryst. Growth Des., 2010, 10,3315–3320.

14 For more information on Ag� � �Ag interactions: (a) A. J. Blake,N. R. Champness, S. S. M. Chung, W.-S. Li and M. Schroder,Chem. Commun., 1997, 1675–1676; (b) Q. Chu, D. C. Swenson andL. R. MacGillivray, Angew. Chem., Int. Ed., 2005, 44, 3569;(c) I. G. Georgiev, D.-K. Bucar and L. R. MacGillivray, Chem.Commun., 2010, 46, 4956–4958.

Fig. 3 ORTEP drawings of (a) TCHD; (b) MCB.

Dow

nloa

ded

by U

nive

rsity

of

Mis

sour

i at C

olum

bia

on 2

1 M

arch

201

3Pu

blis

hed

on 2

2 A

ugus

t 201

1 on

http

://pu

bs.r

sc.o

rg |

doi:1

0.10

39/C

1CC

1399

4K

View Article Online