(Benzene-1,2-diolato-κ2O,O′)(2,2′-bipyridine-κ2N,N′)palladium(II)

Okabe, N.; Aziyama, T.; Odoko, M.

doi:10.1107/S1600536805027704

(Benzene-1,2-diolato-κ²O,O′)(2,2′-bipyridine-κ²N,N′)palladium(II)

In the title complex, [Pd(C₆H₄O₂)(C₁₀H₈N₂)], the central Pd atom has a distorted cis planar four-coordination geometry defined by two O atoms of the benzene-1,2-diolate dianion and the two N atoms of a 2,2′-bipyridine ligand. The molecule is essentially planar.

Read article Similar articles

Supporting information

	Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536805027704/hg6238sup1.cif Contains datablocks global, I
	Structure factor file (CIF format) https://doi.org/10.1107/S1600536805027704/hg6238Isup2.hkl Contains datablock I

CCDC reference: 287594

checkCIF report

Key indicators

Single-crystal X-ray study
T = 296 K
Mean (C-C) = 0.009 Å
R factor = 0.043
wR factor = 0.136
Data-to-parameter ratio = 16.2

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT342_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          9

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion

Comment top

The palladium complex [Pd(bpy)(cbdca)] (where bpy is 2,2'-bipyridine, and cbdca is 1,1-cyclobutanedicarboxylate ligand), with an aromatic ligand and a cis-square planar coordination geometry, has been shown to have better cytotoxic activity than cisplatin, cis-diamminedichloroplatinum(II), against P₃₈₈ lymphocytic leukemia cells (Mansuri-Torshizi et al., 2001).

The planar aromatic ligands may interact easily with DNA, which is the principal target in the chemotherapy of tumors (Shehata, 2001; Cusumano & Giannetto,1997; Neidle et al., 1987).

We have synthesized and determined the crystal structures of several cis-coordinated palladium complexes with aromatic ligands, viz. [Pd(bpy)(cbdca)], [Pb(phen)(cbdca)] (where phen is 1,10-phenanthroline; Muranishi & Okabe, 2004), [Pd(bpy)(nad)], [Pd(biq)(nad)] (where nad is 2,3-naphthalenediol and biq is biquinoline; Okabe et al., 2004) and [Pd(phen)(ca)] (where ca is catechol is 1,2-benzenediol; Okabe et al., 2003). In this study, [Pd(bpy)(ca)], (I), has been synthesized and its structure determined.

In complex (I), the central Pd atom has a distorted cis-square planar coordination geometry with the two N atoms of the heterocycle and the two O atoms of the dianion of the ca ligand (Fig. 1). The overall structure resembles the structures of [Pd(byp)(nad)], (II), and [Pd(phen)(ca)], (III), which have similar bypyridyl and catecholate groups to (I).

The coordinate bond lengths and angles of (I) (Table 1) may be compared with those of (II) and (III), as well as those of other palladium complexes with non-aromatic ligands, suc as [Pd(en)M], (IV), and [Pd(en)C], (V) (where en is ethylenediamine, M is methymalonate and C is 1,1-cyclobutanedicarboxylate; Tercero et al., 2003). The Pd—O and Pd—N bond lengths of (I) resemble those of (II) and (III), in which the Pd—O bond lengths lie in the range 1.981 (2)–1.989 (2) Å and Pd—N in the range 2.001 (3)–2.019 (2) Å, but are slightly shorter than those of (IV) and (V), in which the Pd—O bond lengths lie in the range 1.995 (10)–2.027 (10) Å and Pd—N in the range 2.009 (11)–2.030 (2) Å. The O—Pd—O and N—Pd—N bond angles also resemble to those of (II) and (III), for which O—Pd—O lie in the range 84.84 (9)–85.09 (7)° and N—Pd—N in the range 80.78 (9)–81.69 (8)°, but are a little smaller than those of (IV) and (V), for which O—Pd—O lie in the range 89.51 (17)–92.69 (7)° and N—Pd—N in the range 84.09 (18)–84.15 (8)°. These differences may be explained by the difference in intramolecular mobility of the O and N atoms between the complexes with aromatic ligands and those with non-aromatic ligands, as explained by Okabe et al. (2003).

Experimental top

Bpy (7 mg, 0.0448 mmol) dissolved in dimethyl formamide (DMF, 1.0 ml) was reacted with palladium acetate, [Pd(CH₃COOH)₂] (10 mg), dissolved in DMF (2 ml), and then bpy (5 mg) dissolved in DMF (1 ml) was added. The mixture was allowed to stand at room temperature for a number of days to give red plate crystals of the complex.

Computing details top

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1992); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 2000); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: TEXSAN.

Figures top

Fig. 1. Molecular structure of (I), with the atom-numbering scheme. Displacement ellipsoids for non-H atoms correspond to 50% probability.

(Benzene-1,2-diolato-κ²O,O')(2,2'-bipyridine-κ²N,N')palladium(II) top

Crystal data top

[Pd(C₆H₄O₂)(C₁₀H₈N₂)]	F(000) = 736.0
M_r = 370.70	D_x = 1.840 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.7107 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 7.017 (2) Å	θ = 14.8–15.0°
b = 23.873 (2) Å	µ = 1.39 mm⁻¹
c = 8.118 (3) Å	T = 296 K
β = 100.30 (3)°	Plate, red
V = 1338.0 (6) Å³	0.30 × 0.30 × 0.15 mm
Z = 4

Data collection top

Rigaku AFC-5R diffractometer	R_int = 0.013
ω–2θ scans	θ_max = 27.5°
Absorption correction: ψ scan (North et al., 1968)	h = 0→9
T_min = 0.632, T_max = 0.812	k = 0→31
3414 measured reflections	l = −10→10
3079 independent reflections	3 standard reflections every 150 reflections
2709 reflections with I > 2σ(I)	intensity decay: 0.1%

Refinement top

Refinement on F²	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.043	w = 1/[σ²(F_o²) + (0.0537P)² + 6.095P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.136	(Δ/σ)_max < 0.001
S = 1.21	Δρ_max = 1.94 e Å⁻³
3079 reflections	Δρ_min = −1.62 e Å⁻³
190 parameters

Crystal data top

[Pd(C₆H₄O₂)(C₁₀H₈N₂)]	V = 1338.0 (6) Å³
M_r = 370.70	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 7.017 (2) Å	µ = 1.39 mm⁻¹
b = 23.873 (2) Å	T = 296 K
c = 8.118 (3) Å	0.30 × 0.30 × 0.15 mm
β = 100.30 (3)°

Data collection top

Rigaku AFC-5R diffractometer	2709 reflections with I > 2σ(I)
Absorption correction: ψ scan (North et al., 1968)	R_int = 0.013
T_min = 0.632, T_max = 0.812	3 standard reflections every 150 reflections
3414 measured reflections	intensity decay: 0.1%
3079 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	190 parameters
wR(F²) = 0.136	H-atom parameters constrained
S = 1.21	Δρ_max = 1.94 e Å⁻³
3079 reflections	Δρ_min = −1.62 e Å⁻³

Special details top

Refinement. Refinement using reflections with F² > −10.0 σ(F²). The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Pd1	0.76643 (5)	0.00981 (2)	−0.00121 (4)	0.0268 (1)
O1	0.8946 (6)	0.0700 (2)	0.1488 (4)	0.0322 (8)
O2	0.7077 (5)	0.0696 (2)	−0.1718 (4)	0.0327 (8)
N1	0.8064 (6)	−0.0532 (2)	0.1643 (5)	0.0299 (9)
N2	0.6366 (6)	−0.0518 (2)	−0.1446 (5)	0.0292 (9)
C2	0.7272 (7)	−0.1027 (2)	0.1075 (6)	0.030 (1)
C3	0.7401 (8)	−0.1490 (3)	0.2116 (7)	0.038 (1)
C4	0.8380 (9)	−0.1436 (3)	0.3763 (7)	0.042 (1)
C5	0.9177 (9)	−0.0929 (3)	0.4326 (7)	0.045 (1)
C6	0.9021 (9)	−0.0494 (3)	0.3221 (7)	0.039 (1)
C12	0.6294 (7)	−0.1019 (2)	−0.0683 (6)	0.031 (1)
C13	0.5358 (8)	−0.1469 (3)	−0.1540 (7)	0.037 (1)
C14	0.4500 (9)	−0.1404 (3)	−0.3204 (7)	0.041 (1)
C15	0.4604 (9)	−0.0899 (3)	−0.3978 (7)	0.043 (1)
C16	0.5546 (9)	−0.0459 (3)	−0.3072 (7)	0.040 (1)
C17	0.8803 (7)	0.1186 (2)	0.0639 (6)	0.029 (1)
C18	0.9567 (8)	0.1683 (3)	0.1350 (7)	0.037 (1)
C19	0.9308 (9)	0.2184 (3)	0.0443 (8)	0.043 (1)
C20	0.8272 (9)	0.2185 (3)	−0.1180 (8)	0.043 (1)
C21	0.7530 (8)	0.1686 (3)	−0.1925 (7)	0.037 (1)
C22	0.7783 (7)	0.1188 (2)	−0.1039 (6)	0.029 (1)
H3	0.6847	−0.1829	0.1726	0.0455*
H4	0.8493	−0.1743	0.4481	0.0508*
H5	0.9804	−0.0885	0.5428	0.0544*
H6	0.9606	−0.0155	0.3580	0.0465*
H13	0.5302	−0.1811	−0.1006	0.0444*
H14	0.3857	−0.1703	−0.3792	0.0490*
H15	0.4049	−0.0853	−0.5099	0.0514*
H16	0.5616	−0.0115	−0.3593	0.0481*
H18	1.0258	0.1684	0.2440	0.0442*
H19	0.9830	0.2515	0.0928	0.0521*
H20	0.8071	0.2520	−0.1773	0.0521*
H21	0.6862	0.1687	−0.3023	0.0447*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Pd1	0.0307 (2)	0.0266 (2)	0.0221 (2)	0.0011 (1)	0.0019 (1)	−0.0011 (1)
O1	0.044 (2)	0.030 (2)	0.021 (2)	−0.002 (2)	−0.001 (1)	0.000 (1)
O2	0.039 (2)	0.030 (2)	0.025 (2)	−0.002 (2)	−0.003 (1)	0.000 (1)
N1	0.030 (2)	0.035 (2)	0.024 (2)	0.001 (2)	0.004 (2)	−0.001 (2)
N2	0.030 (2)	0.036 (2)	0.021 (2)	0.001 (2)	0.003 (2)	−0.002 (2)
C2	0.028 (2)	0.039 (3)	0.023 (2)	0.001 (2)	0.005 (2)	0.000 (2)
C3	0.040 (3)	0.041 (3)	0.029 (3)	−0.004 (2)	−0.001 (2)	0.004 (2)
C4	0.055 (4)	0.043 (3)	0.027 (3)	−0.001 (3)	0.001 (2)	0.009 (2)
C5	0.050 (3)	0.056 (4)	0.026 (3)	−0.001 (3)	−0.001 (2)	0.002 (3)
C6	0.046 (3)	0.039 (3)	0.028 (3)	−0.004 (2)	−0.001 (2)	−0.004 (2)
C12	0.029 (2)	0.036 (3)	0.027 (2)	0.002 (2)	0.003 (2)	−0.001 (2)
C13	0.041 (3)	0.040 (3)	0.029 (3)	−0.002 (2)	0.003 (2)	−0.002 (2)
C14	0.050 (3)	0.042 (3)	0.028 (3)	−0.007 (3)	0.000 (2)	−0.008 (2)
C15	0.051 (3)	0.046 (4)	0.027 (3)	−0.004 (3)	−0.004 (2)	−0.004 (2)
C16	0.049 (3)	0.041 (3)	0.027 (3)	−0.002 (2)	−0.003 (2)	−0.001 (2)
C17	0.028 (2)	0.033 (3)	0.024 (2)	0.002 (2)	0.001 (2)	−0.002 (2)
C18	0.039 (3)	0.043 (3)	0.026 (2)	−0.004 (2)	−0.002 (2)	−0.006 (2)
C19	0.047 (3)	0.037 (3)	0.042 (3)	−0.007 (2)	−0.004 (3)	−0.007 (2)
C20	0.052 (3)	0.034 (3)	0.041 (3)	0.000 (2)	−0.002 (3)	0.008 (2)
C21	0.040 (3)	0.041 (3)	0.027 (3)	0.001 (2)	−0.006 (2)	0.007 (2)
C22	0.031 (2)	0.033 (3)	0.023 (2)	0.003 (2)	0.001 (2)	−0.002 (2)

Geometric parameters (Å, º) top

Pd1—O1	1.992 (4)	C12—C13	1.380 (8)
Pd1—O2	1.980 (4)	C13—C14	1.386 (8)
Pd1—N1	2.003 (4)	C13—H13	0.930
Pd1—N2	1.993 (4)	C14—C15	1.367 (9)
O1—C17	1.345 (7)	C14—H14	0.930
O2—C22	1.354 (6)	C15—C16	1.381 (9)
N1—C2	1.352 (7)	C15—H15	0.930
N1—C6	1.339 (7)	C16—H16	0.930
N2—C12	1.351 (7)	C17—C18	1.385 (8)
N2—C16	1.350 (7)	C17—C22	1.421 (7)
C2—C3	1.384 (8)	C18—C19	1.398 (9)
C2—C12	1.469 (7)	C18—H18	0.930
C3—C4	1.396 (8)	C19—C20	1.386 (8)
C3—H3	0.930	C19—H19	0.930
C4—C5	1.376 (9)	C20—C21	1.395 (9)
C4—H4	0.930	C20—H20	0.930
C5—C6	1.365 (9)	C21—C22	1.384 (8)
C5—H5	0.930	C21—H21	0.930
C6—H6	0.930

Pd1···Pd1ⁱ	3.308 (1)	C2···C17ⁱ	3.322 (8)
Pd1···N2ⁱⁱ	3.406 (5)	C2···C22ⁱ	3.496 (7)
Pd1···O1ⁱ	3.427 (4)	C2···C22ⁱⁱ	3.563 (7)
O1···N2ⁱ	3.325 (6)	C2···C18ⁱ	3.579 (8)
O1···C14ⁱⁱ	3.437 (8)	C3···C21ⁱⁱ	3.468 (8)
O1···C5ⁱⁱⁱ	3.462 (7)	C4···C21ⁱ	3.514 (9)
O1···C15ⁱⁱ	3.509 (8)	C6···C22ⁱ	3.512 (8)
O1···C13ⁱⁱ	3.540 (7)	C12···C22ⁱⁱ	3.426 (8)
O1···N1ⁱ	3.597 (6)	C12···C18ⁱ	3.436 (8)
O1···C12ⁱ	3.598 (7)	C12···C17ⁱ	3.457 (7)
O2···C6ⁱ	3.227 (8)	C13···C17ⁱⁱ	3.206 (8)
O2···C2ⁱⁱ	3.284 (7)	C13···C22ⁱⁱ	3.368 (8)
O2···C12ⁱⁱ	3.412 (7)	C13···C18ⁱⁱ	3.524 (8)
O2···N1ⁱ	3.422 (6)	C13···C18ⁱ	3.574 (8)
O2···C15^iv	3.516 (7)	C14···C17ⁱⁱ	3.421 (8)
N1···C22ⁱ	3.420 (7)	C14···C18ⁱⁱ	3.520 (9)
N1···C17ⁱ	3.487 (7)

O1—Pd1—O2	85.6 (1)	C2—C12—C13	125.2 (5)
O1—Pd1—N1	97.9 (2)	C12—C13—C14	119.3 (6)
O1—Pd1—N2	178.1 (2)	C12—C13—H13	120.4
O2—Pd1—N1	175.7 (2)	C14—C13—H13	120.4
O2—Pd1—N2	96.2 (2)	C13—C14—C15	119.8 (6)
N1—Pd1—N2	80.3 (2)	C13—C14—H14	120.1
Pd1—O1—C17	109.0 (3)	C15—C14—H14	120.1
Pd1—O2—C22	109.0 (3)	C14—C15—C16	119.0 (5)
Pd1—N1—C2	115.3 (3)	C14—C15—H15	120.5
Pd1—N1—C6	125.2 (4)	C16—C15—H15	120.5
C2—N1—C6	119.5 (5)	N2—C16—C15	121.4 (6)
Pd1—N2—C12	115.9 (3)	N2—C16—H16	119.3
Pd1—N2—C16	124.4 (4)	C15—C16—H16	119.3
C12—N2—C16	119.7 (5)	O1—C17—C18	122.6 (4)
N1—C2—C3	120.8 (4)	O1—C17—C22	118.2 (5)
N1—C2—C12	114.3 (5)	C18—C17—C22	119.2 (5)
C3—C2—C12	124.9 (5)	C17—C18—C19	120.6 (5)
C2—C3—C4	118.6 (6)	C17—C18—H18	119.7
C2—C3—H3	120.7	C19—C18—H18	119.7
C4—C3—H3	120.7	C18—C19—C20	120.0 (6)
C3—C4—C5	120.0 (6)	C18—C19—H19	120.0
C3—C4—H4	120.0	C20—C19—H19	120.0
C5—C4—H4	120.0	C19—C20—C21	120.1 (6)
C4—C5—C6	118.2 (5)	C19—C20—H20	120.0
C4—C5—H5	120.9	C21—C20—H20	120.0
C6—C5—H5	120.9	C20—C21—C22	120.3 (5)
N1—C6—C5	123.0 (6)	C20—C21—H21	119.8
N1—C6—H6	118.5	C22—C21—H21	119.8
C5—C6—H6	118.5	O2—C22—C17	118.2 (5)
N2—C12—C2	114.1 (5)	O2—C22—C21	122.0 (4)
N2—C12—C13	120.7 (5)	C17—C22—C21	119.8 (5)

Pd1—O1—C17—C18	−179.8 (4)	N1—C6—C5—C4	2.8 (10)
Pd1—O1—C17—C22	1.9 (6)	N2—PD1—O2—C22	178.5 (3)
Pd1—O2—C22—C17	1.9 (6)	N2—PD1—N1—C2	−2.2 (4)
Pd1—O2—C22—C21	−177.8 (4)	N2—PD1—N1—C6	178.2 (5)
Pd1—N1—C2—C3	−178.1 (4)	N2—C12—C2—C3	−179.8 (5)
Pd1—N1—C2—C12	1.5 (6)	N2—C12—C13—C14	0.6 (9)
Pd1—N1—C6—C5	176.9 (5)	N2—C16—C15—C14	0.2 (10)
Pd1—N2—C12—C2	−2.5 (6)	C2—N1—C6—C5	−2.7 (9)
Pd1—N2—C12—C13	177.3 (4)	C2—C3—C4—C5	0.6 (10)
Pd1—N2—C16—C15	−177.5 (5)	C2—C12—N2—C16	179.0 (5)
O1—PD1—O2—C22	−0.7 (3)	C2—C12—C13—C14	−179.7 (6)
O1—PD1—N1—C2	177.0 (4)	C3—C2—N1—C6	1.5 (8)
O1—PD1—N1—C6	−2.6 (5)	C3—C2—C12—C13	0.5 (9)
O1—C17—C18—C19	−177.1 (5)	C3—C4—C5—C6	−1.6 (10)
O1—C17—C22—O2	−2.7 (7)	C4—C3—C2—C12	179.9 (6)
O1—C17—C22—C21	177.0 (5)	C6—N1—C2—C12	−178.8 (5)
O2—PD1—O1—C17	−0.7 (3)	C12—N2—C16—C15	0.9 (9)
O2—PD1—N2—C12	−174.9 (4)	C12—C13—C14—C15	0.5 (9)
O2—PD1—N2—C16	3.6 (5)	C13—C12—N2—C16	−1.3 (8)
O2—C22—C17—C18	178.9 (5)	C13—C14—C15—C16	−0.9 (10)
O2—C22—C21—C20	179.7 (5)	C17—C18—C19—C20	0.3 (10)
N1—PD1—O1—C17	−178.1 (3)	C17—C22—C21—C20	0.0 (9)
N1—PD1—N2—C12	2.6 (4)	C18—C17—C22—C21	−1.4 (8)
N1—PD1—N2—C16	−178.9 (5)	C18—C19—C20—C21	−1 (1)
N1—C2—C3—C4	−0.5 (9)	C19—C18—C17—C22	1.3 (9)
N1—C2—C12—N2	0.6 (7)	C19—C20—C21—C22	1.5 (10)
N1—C2—C12—C13	−179.1 (5)	C19—C20—C21—C22	1.5 (10)

Symmetry codes: (i) −x+2, −y, −z; (ii) −x+1, −y, −z; (iii) −x+2, −y, −z+1; (iv) −x+1, −y, −z−1.

Experimental details

Crystal data
Chemical formula	[Pd(C₆H₄O₂)(C₁₀H₈N₂)]
M_r	370.70
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	296
a, b, c (Å)	7.017 (2), 23.873 (2), 8.118 (3)
β (°)	100.30 (3)
V (Å³)	1338.0 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	1.39
Crystal size (mm)	0.30 × 0.30 × 0.15

Data collection
Diffractometer	Rigaku AFC-5R diffractometer
Absorption correction	ψ scan (North et al., 1968)
T_min, T_max	0.632, 0.812
No. of measured, independent and observed [I > 2σ(I)] reflections	3414, 3079, 2709
R_int	0.013
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.136, 1.21
No. of reflections	3079
No. of parameters	190
No. of restraints	?
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.94, −1.62

Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1992), MSC/AFC Diffractometer Control Software, TEXSAN (Molecular Structure Corporation, 2000), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 1997), ORTEPII (Johnson, 1976), TEXSAN.

Selected geometric parameters (Å, º) top

Pd1—O1	1.992 (4)	Pd1—N2	1.993 (4)
Pd1—O2	1.980 (4)	O1—C17	1.345 (7)
Pd1—N1	2.003 (4)	O2—C22	1.354 (6)

O1—Pd1—O2	85.6 (1)	O2—Pd1—N1	175.7 (2)
O1—Pd1—N1	97.9 (2)	O2—Pd1—N2	96.2 (2)
O1—Pd1—N2	178.1 (2)	N1—Pd1—N2	80.3 (2)

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Text
		Plain Text

Format		BIBTeX
		EndNote
		RefMan
		Refer
		Medline
		CIF
		SGML
		Text
		Plain Text

Search IUCr Journals		doi		Advanced search
Author		volume	page