Indian Journal of ChemistryVol. 22A, February 1983, PP. 154-155

Nucleoside Monophosphate Complexes ofDioxouranium(VI)

K RAMALINGAM & C R KRISHNAMOORTHY*

Department of Chemistry, Indian Institute of Technology,Madras 600 036

Received 29 April 1982; revised and accepted 16 October 1982

Complexes of UO;+ with adenosine-St-monophosphoric(5'-AMP), cytidine-5'-monophosphoric (5'-CMP), guanosine-5'-monophosphoric (5'-GMP), inosine-S'-monophosphoric(S'-IMP) and uridine-St-monophosphoric (S'-UMP) acidshave been prepared and characterized on the basis of IR, farIR and TG analyses. The involvement of phosphate moietyof the ligands in binding to UO~+ is noticed in all the cases.Besides, metal ion binding through ring nitro gens such as N-7in AMP, N-3 in CMP, N-7 in GMP and IMP is also evidentfrom IR data. TG analyses of the complexes confirm thenumber of water molecules in the complexes.

In continuation of our earlier work on mixed ligandcomplexes of UO~+ and ThH with purine, pyrimidinebases and nucleosides in solution", we report in thisnote the isolation and characterisation of a seriesof nucleoside-S' -monophosphate complexes ofdioxouranium (VI).

Disodium salts of adenosine-5'-monophosphoric(5'-AMP), guanosine-5' -monophosphoric (5'-GMP),inosine-S' -monophosphoric (5'-IMP), uridine-S'-monophosphoric (5'-UMP) and cytidine-S'smono-phosphoric (5'-CMP) acids used were of high purity(extrapure, SRL).

Equivolume of equimolar solutions of nucleosidemonophosphates and uranyl nitrate (E. Merck) indeionized water were mixed, warmed on a water-bath for 15 min and cooled. The yellow complexesformed were filtered, washed several times with smallportions of water and finally with acetone and driedin vacuo at room temperature for 6-8 hr.

The IR spectra were recorded on Perkin-Elmermodel 257 and Fourier far IR 30 spectrophotometers.The characteristic ring vibrations of 5'-AMP in theregion 1600-1700cm-l are shifted to higher frequencyon complexation indicating coordination of adeninering probably through N-7 (see ref. 2 also). ThevC=O of 5'-GMP at 1685 cm-l is not onlyshifted to 1680 cm-t, but a new band also appearsat 1625 cm-1 upon complexation with UO~+. TheCs-H out-of-plane vibration appearing e-- 780 cm-lis shifted to lower frequency indicating the involve-ment of neighbouring N-7 in complex formation.In the case of 5'-IMP, vC=O at 1972 em-I shiftsto higher wave number (1690 em-I) on complexation.The Cs-H out-of-plane vibration frequency under-goes a downward shift indicating the probableinvolvement of N-7 in coordinations.

In the case of 5'-CMP a broad IR band appear-ing in the region 1680 to 1720 cm-I corresponds- tomerged absorption bands of NH2 deformation andvC=O. This band splits into separate ones oncomplexation. Moreover Na-H deformation vibra-tion appearing at 1550 cm-1 loses its intensity oncomplexation, suggesting that the coordination mayinvolve N-3, as has been seen earlier", In the caseof 5'-UMP, vC=O at 1670 cm? is shifted to 1700em"? and N-H deformation at 1480 cm-I is shiftedto 1470 em'< showing the involvement of ring moietyin coordination.

In the IR spectra of all the complexes studied thebands in the region 900-1000 cm-l undergo extensivebroadening suggesting the possibility of hydrogenbonded interactions with the metal ions", Thev(C)-O-P of the free ligands which appear around800 crrr-', are shifted to higher wave numbers(,6.v=20 crrr-') in almost all the complexes oncomplexation, indicating the strengthening of esterbond. Also phosphate asymmetric stretching offree ligands around 975 crrr=! is shifted to higherfrequency on coordination with UO~+ ion. The v asO-U-O in all the complexes appears as strong peaks,....910cm? whereas the same appears at 930 cm-1in free uranyl nitrate. The above shift to lower

Table I-Elemental and TG Analyses DataFound (calc) %

36.4 17.7(36.9) (16.4)38.6 16.3(39.1) (15.6)38.1 17.0

(38.4) (17.1)39.0 17.S

(39.2) (17.4)41.3 15.7

(41.8) (16.7)tUO~+ was estimated by spectrophotometric method".tCalculated from TG analyses by assuming the formation of pyrophoshate at a temperature> 700°C.

Compound

UOi(AMPH) N03.3H.O

U02(CMPH) N03·2H.O

U02GMP.4H~O

UO.UMP.3H.O

C H N Mass Iosst

2.S(2.6)2.4

(2.4)2.5

(2.8)2.4

(2.8)2.4

(2.6)

10.8(11.4)

8.1( 8.1)

9.6( 9.9)

8.1( 8.1)

4.2( 4.3)

50.11(48.75)48.76(S1.72S1.37)

(SO.76)51.69

(51.87)5S.53

(S5.2S)

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frequency on complexation of uranyl ion is documen-ted earlier". Far IR spectra of the complexes showweak peaks at 260 and 270 cm-1 characteristic ofdoubly degenerate deformation vibrations of UO~+ion in the complexes.

Thermal analyses (Stantson TG balance; heatingrate 6°jmin) of the complexes show loss of waterupto 220°C. In all the complexes decompositionstarts around 200°C and no clear steps are observedto characterize the decomposing moiety. The massloss determined by TG analyses of the complexes 3agrees very well with the proposed formulae given 4in Table 1. The analysis of the green colouredresidue confirms that it is uranyl pyrophosphate. 5

Moreover IR study indicates the involvement of 6both the ring and phosphate moieties in metal 7coordination. Similar studies with Th4+ ion is underprogress.

NOTES

The authors thank Prof Rudi Van Eldik for theelemental analyses and one of the authors (KR)thanks the CSIR, New Delhi for the award of ajunior research fellowship.

References

Ramalingam K & Krishnamoorthy C R, Inorg chim Acta,(in press).

2 Collins A D, de Meester P, Goodgame D M L & SkapskiA C, Biochim Biophys Acta, 402 (1975) 1.

Aoki K, Bull chem Soc Japan, 48 (1975) 1260.Angell C L, J chem Soc, (1961) 504.Clark G R & Orbell J D, Chem Commun, (1975) 697.Clark G R & Orbell J D, Chem Commun, (1974) 139.Manzotto A, Nicolini M, Brago F & Pinto G, Inorg chim

Acta 34 (1979) L 295.8 Savin S B, Ta/anta, 8 (1961) 673.

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