Gupta, S P Sen

Kar, Tanusree

English

IACS Institutional Repository

Indian J. Phys. 6 6 A (5). 645-651 (1992)Structural studies on some basic ligands : precursors for synthesising binuclear metal complexesTanusree Kar and S P Sen GuptaDepartment of Materials Science, Indian Association forllie Culuvation of Science,Jadavpur, Calcutta -  700 032, IjidtaReceived 16 September 1991, accepted 25 September 1991Abstract : Results of the stniciural and molecular studies of three basic ligands namely, (I) 2-hyd^oxy~5-^nelhyl~isophthalaldchydc C9Hg0 3 . (H) 2-acctyl-6 -bcn7x)yal-4-Tnethyl phenol ^16^14^3 on) 2,6~dibutyryl-4-mcihyl phenol €{5112003.. which are precursors for synthesising macrocyclic ligands, arc reported here alongwiih a discussion on other related compounds which exist in the literature. All the three compounds are characterized by a strong intra-molecular hydrogen bonding, which becomes stronger with the elongation of side chains. It is further apparent that, with the.additions of bulky groups or side chains, the compoundstransfonn to lower symmetry (1 c. orthorhombic---- ► monoclinic---- > tnclinic) as far as thecrystalline lattice stniciure is concerned.Keywords : Orgamc compounds, conformations, intra-molecular hydrogen bonding.PACS Nos. : 61-10.-1, 61.10.My1. In troduction  : Chemical AspectsU has become interesting to "study the bi-nuclear metal complexes derived from the condensation products o f 4-methyl~2,6-diformyI phenol [1] with various bi- and poly functionized molecules [1-3]. These studies were made to address basically to have (i) correlation o f magnetic interactions with structural parameters, (ii) selective fixation and transport o f substrates, (iii) catalysis of multicentcr-multielccironic processes, and (iv) condensation o f different substrates brought together and held in proximity. More recently, there is growing awareness, to design suitable binuclear copper(II) complexes that would fnimic the behaviour of emigmatic type 3 copper proteins particularly homocyamin [4-9].It may be mentioned that all the reported studies are concerned with the metal complexes derived from the condensation products of 4-methyl-2,6-diformyl phenol, but nothing is known about other homologucs namely, 4-methyl-2,6-diacyl/bcnzoyl phenol. In our Inorganic Chemistry division of this Insiiluic, Mondal and Nag [10-12] have undertaken an extensive programme of investigating binuclear complexes of later homologucs. In the scheme (Figure 1) synthetic strategics that have been adopted by these workers to generate binuclear coppcr(II) complexes have been outlined. Compounds of the© 1992 lACStype (4) contain two strongly antifcrromagnctically coupled coppcr(II) ions and they undergo single step two-electron transfers [10], the features typical of EPR-silent copper(II) proteins. Contrary to these, complexes of the type 5, in which also copper(ll) ions arc very strongly coupled, however, undergo sequential electron transfers at two different potentials [11].646 Tanusree Kar and S P Sen GuptaFigure 1. SynlhciK siraicgics lo gcncraic binuclcar copper complexComplexes of the type (7) contain highly llcxiblc ligand environment and therefore, would be expected to have interesting structural features. Structural analysis of the complexes (4) would be also highly desirable in as much as the two copper atoms are not in identical environment. Redox behaviour of the other type of complexes have turned out lo be interesting and it has been shown from electrochemical vis-a-vis magnetic studies that in the coupled systems the triplet not the singlet state undergoes reduction [11]. In order to understand major as well as subtle difference in reactivity of these complexes, structural information about these species arc very much essential.In the light of all the above consideration, a scries of structural investigations with these compounds have been undertaken by the present authors in the X-ray laboratory in collaboration with the chemistry division. This presentation summarizes the structural and molecular studies of the following three basic ligands namely,(I) 2-hydroxy-5-meihyb isophihalaldchydc-C9Hj5 0 3  (Figure 2), [131(II) 2-acctyl-fvbcn/oyl-4- methyl phcnol-C|6 H| 4 0 3  (Figure 3), [14](III) 2,6-dibulyryl-4-mcthyl phcnol-Cj5 H2 ()0 3  (Figure 4), 115]The second and third compounds arc the extensions of the first one in which the twohydrogen atoms in 13 positions arc replaced by the different chemically active groups. The compounds arc also imp)ortant in synthesising macrocylcs which would accommodate metalStructural studies on some basic ligands etc. 647FImire 2. Ortep plot of 2 hydroxy-5-mcihyl isophihalalciihydc,Flj»ure 3 Oricp ploi ol 2-aceiyl-6-bcnA>ydI 4 mclhyl phenol, C i6 » m 03-atoms and serve as useful biologicaJ models. Cell constants and other crystal parameters for ihe compounds arc summarized in Table 1. The intensity data (L-P corrected) for all the three compounds were collected on a CAD-4 Enraf-Nonius dillractomcter at the RSIC (Bose Institute, Calcutta). All the structures have been solved by Direct methods using the programmes MULTAN-78 116] and MULTAN-80 [171. The relevant bond lengths (standard deviations in the range of 0.005 -  0.01 A) and planarity of the molecules for all the three compounds arc summarized in Tabic 2.Tabic 1. Crystal data.648 Tanusree Kar and S P Sen GuptaParameters Compound I Compound II Compound IIIMolecular formula C j i iA C13H20Q3A (A) 0.7114 0.7114 0.7114« (A) 25.998(8) 11.836(5) 8.12(1)b (A) 7.555(2) 8.706(2) 9.39(1)c (A) 3.944(2) 15.365(4) 10.31(0)0a 90 90 103.590 123.05(3) 91.90Y 90 90 114.1(1)K(A)3 m . l { 5 ) 1327.09 690.84D  cal g cm 1.41 1.27 1.19Z 4 4 2Space group P2 2 2 1 1 1 P 21 /c P *1No of observedreflcaionsF o > 2  a (F o) 526 1587 804/^-factor (%) 9.1 6.7 9.92 . Results and discussionsAll the three structures arc characterized by a very suong inira-molecular hydrogen bonding between pticnolic oxygen and the carbonyl oxygen in conrormily with the NMR and IRFigure 4. Ortep ploi of2*6-dibuiyryl-4-mcihyl phenol, C jjll2o^3*spectra. This bonding is strongest for the compound III having lowest summetry (Pi). Though the chemically equivalent bond distances within the six membered rings arcidenlical, they have, however, undergone a slight deformation from the normal bwizene ring geometry and this may be attributed to the effect of substituents. In compound II, though both the aromatic rings are equivalent in respect of bond lengths, the angular deviations in ring B are much more pronounced that those in ring A, and this may be due to the presence of more number of substituents in the molecules. The relation between the angular deviations and substituents effect was studied for compounds with mono- and di-subslitutedTable 2. Relevant bond distance (A) and planarity of benzene rings.Structural stud ies on som e basic Uganda etc. 649Pirameten Compound I Compound II Compound inC(Sp^>-C(Sp^) distancebetween methyl carbon 1.55 1.54 1.54and aromatic ring carbonAverage C(Sp^ -  C(Sp^) NoC(Sp*)-C(Sp»)disunce in the side bond in the side 1.47 1.49chains chainAverage C(Sp^)-C(Sp^)distance between aromatic 1.46 1.48 1.46ring carbon and carbonylcarbonAverage C ~ C distance inthe benzene rmg 1.39 1.30 1.40Average C = O distance 1.21 1.22 1.22C-OH 1.36 1.36 1.35Intra-mdccular hydrogenbonding distance between 2.62 2.55 2.46phendic oxygen andcarbonyl oxygenPlanarity Benzene ring is almost Both the benzene Benzene ring itplanar maximum nngs arc planar planar, maximumdeviation -0.02 A and they arc inch- deviation -0.01 Aned with each otherat an angle 108.8^benzene rings [18, 19]. Another significant observation in all the three stfuctures is the deviations of C—OH and C=0 bond distances from their expected values, which can be explained by considering electron donation from hydroxyl group through the aromatic system to the carbonyl group which in turn strengthens the C—OH bond, weekens the C O bond, and increases the negative charge on the carbonyl oxygen [20] resulting in an intra­molecular hydrogen-bonding causing a shortening in the C—OH bond and lengthening in C =0 bond ffom their normal values. Similar observation can be had. for example, in the structure of 2 ,2 '-dihydioxy benzophenone [20]. In all the above cases the C=0 distance is legthened against the normal value (C=0) = 1.20 A. The other efsp^) _ efsp^) distances inthe side chains show small positive and negative deviations from the nomtal expected value. The unusual short value (1.24 A) for the distance between (C12 and CI4) atoms towards the free end of one of the side chains in compound III, could only be attributed to the limited size of data and also to some disordering in the molecule, as evident from high thermal parameters (ORTEP PLOT, Figure 4) for the atoms concerned. The type of bond slustening with higher thermal parameters for atoms concerned have also been encountered in other structures [21, 22]. The planarity calculations show that the structure of compound I is almost planar. The planes of the two phenyl rings in compound II are inclined at an angle of 108.8°. This inclination is, however, expected since it tends to minimize the tc -  n orbital overlap between the rings, and compares favourably with values observed in other diphenyl methane structure [23, 24], In all the three structures, the molecules did not involve themselves with any inter-molecular hydrogen bonding, and all the structures are completely stabilized by the normal van dcr Waals forces.3 . C o n c lu s io n s(a) The'molecular structure of all the three compounds (1, II, III) presented here have similar conformations as far as bond distances and angles are concerned.(b) All the three structures are characterized by a strong intra-molecular hydrogen bonding and this bonding becomes su'onger with the elongation of side chains (Compounds III). In the molecular packing there exists no inter-molecular contact involving hydrogen and the su-uctures are stabilized by normal inter-atomic forces.(c) With the additions of bulky groups or side chains, the structures transform tolower symmetry (i.e. orthorhombic-----> monoclinic-----> triclinic).650 Tanusree Kar and S P Sen GuptaA cknow ledgm entWe thank Professor K Nag and his colleagues of the Inorganic'Chemistry Division, Indian Association for the Cultivation of Science for providing single crystals of the compounds and many helpful discussions.ReferencesmPI PIU Casscllato, P Vigato and M Vidali 1977 C o ord . C hem  R e v  23 31 S E Groh 1976 fnorg. Chem. 15 227U Casellato, P Vigaio. D E Fenton and M Vidali 1979 Chem Soc Rev, 8 199[4] R R Gagne, C A Koral, T J Smith and M C Cimolino 1979a J Chem. Soc 101 4571(5] R R Gagne. R P Krch and J A Dodge 1979b J Chem Soc 101 6917H  R R Gagne. L M Hemling and J Kisicnmacher 1980 Inorg. Chem. 19 1226(7J R R Gagne. C L Spiro. T J Smith, W R 'Dues and A K Shiemke 1981 / . Am. Chem. Soc. 103 4073 [81 J Graybowski, P H Merrell and F L Vrback 1978 Jnorg Chem. 17 3078 (9] J Grazybowski and F L Urbach 1980 Inorg. Chem 19 2604 [101 S K Mondal and K Nag 1983a Inorg Chem 22 2567 [111 S K Mondal and 1C Nag 1983b J. Chem. Soc lyulton Trans. 2439 [121 S K Mondal and K Nag 1984 J. Chem. Soc. Dulion Trans. 2839 [131 Tranusrec Ray and S P Sen GupU 1982 Cryst. Struct. Commun 11 59Stnictural studies on some basic ligands etc. 651[14][15] [161[17][18][19][20] [21] [22][23][24]Tanutite Ray and S P Sen Gupla 1981 Cryst. Sirycl. Commun. 101123 Taniuree Ray and S P Sen Gupu 1986 Indian J. Phys. 60A 110P Main, S E Hull, L Lessinger, G Gennain, I P Dcclercq and M M Woolfson 1978 MULTAN 78. A system  o f  computer programmes fo r the Automatic Solution o f Crystal Structures from X-ray Diffraction Data (Universities of York and Louvain, England)P Main, S J Rske, S E Hull, L Lessinger, G Germain, J P Declercq and M M Woolfson 1980 MULTAN 80. A system o f  computer programmes for the Automatic Solution o f Crystal Structure from X-ray Diffraction Data (Universities of York and Ijouvain, England)A Domcnicano, A Viciago and C A Coulson 1975 Acta Cryst B31221 A Domenicano, P Mazzeo and A Vaciago 1976 Tetrahedral Lett 13 1029 E 0 Schlemper 1982 Acta. Cryst. B381619M R Smith, R A Zingaro and E A Meyers 1971 7 Organomeial Chem 27 341 Y Lc Page, E J Gabc, L R C Berclcy and J M Dust 1981 Acta Cryst. B37 976 B Chaudhun and A Hargreaves 1956 Acta Cryst 9 793 E J W Whittaker 1953 Acta C’ry.vr 6 714

Structural Studies on some Basic Ligands : Precursors for Synthesising Binuclear Metal Complexes

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Structural Studies on some Basic Ligands : Precursors for Synthesising Binuclear Metal Complexes

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