1,3-Bis(2,2':6',2''-terpyridin-4'-yl)­benzene, a new dinucleating bis­(tridentate) ligand, as its dichloromethane solvate

The title compound, 1,3-bis(2,2':6',2''-terpyridin-4'-yl)­benzene di­chloro­methane solvate, C₃₆H₂₄N₆·CH₂Cl₂, is a new ligand suitable for bridging two metal centres. Though not in binding conformations, its two ter­pyridine units are linked in a unique arrangement, through a meta-phenyl­ene core, which disallows resonance communication between binding sites, as reflected by the crystal structure of its 1:1 CH₂Cl₂ solvate. The two ter­pyridine units are related by crystallographically imposed twofold symmetry, forming a 30.02 (8)° dihedral angle with the phenyl­ene core, but with fairly coplanar pyridine rings within. The solvent mol­ecule is disordered over the twofold axis.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.004 Å
• Disorder in solvent or counterion
• R factor = 0.063
• wR factor = 0.175
• Data-to-parameter ratio = 12.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



RINTA_01  Alert C The value of Rint is greater than 0.10
          Rint given   0.107

PLAT_302  Alert C Anion/Solvent Disorder .......................      40.00 Perc.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

---

S1. Comment

1,4-Bis(2,2':6',2''-terpyridin-4'-yl)benzene, the so-called `back-to-back' bis(terpyridine), is known (Kröhnke, 1976; Constable & Thompson, 1992; Vaduvescu & Potvin, 2002) and has been used as a bridging ligand in multinuclear complexes of Ru and other metals (Collin et al., 1993; Barigelletti et al., 1994; Janini et al., 1999; Vaduvescu & Potvin, 2002), but has apparently not appeared in any crystal structure. The title compound, (I), is the meta-linked isomer, prepared to study the electrochemical and spectroscopic properties of the analogous di- and trinuclear Ru complexes lacking a resonance route of communication between metal centres. The effect of this lack of resonance on the structure of the free ligand was therefore of interest.

Compound (I) was easily prepared by a one-pot synthesis from isophthalaldehyde, 2-acetylpyridine and NH₄OAc, a remarkable reaction in which seven molecules condense at once. The yield (37%) is comparable to yields obtained for the para-phenylene-linked isomer.

Compound (I) co-crystallized with CH₂Cl₂ in the Pccn space group. The molecule resides on a twofold axis which runs through atoms C1 and C4 of the central phenyl ring. The solvate is also disordered over a twofold axis. The terpyridine units are in a non-chelating conformation to avoid electron-pair repulsions. The three pyridine moieties in each unit are fairly coplanar [interplanar dihedral angles 8.81 (15) and 8.04 (16)°], but the phenylene linker is twisted 30.02 (8)° out of coplanarity from the central pyridine. The bond lengths are as expected, with no statistical difference among the three inter-ring bonds, which, along with the ca 30° twist, is consistent with a lack of significant π-communication.

S2. Experimental

2-Acetylpyridine (1.00 g, 8.3 mmol) was added to a solution of isophthalaldehyde (0.2764 g, 2.1 mmol) in CH₃OH (100 ml). Then 15% aqueous KOH (2.3 ml) and concentrated NH₄OH (23 ml) were added to the solution. Vigorous stirring was maintained at reflux for 2 d. The yellow precipitate that formed was isolated by vacuum filtration, washed with water to neutral pH and dissolved in CHCl₃ (40 ml). The solution obtained was washed with H₂O (3 × 30 ml). The organic fraction was dried with MgSO₄ and the solvent removed in vacuo. The residue was recrystallized in CHCl₃/Et₂O, yielding 0.4109 g (37%), m.p. >573 K. δ_H (CDCl₃) 8.84 (s, 4H), 8.77 (d, 4H, J = 5.3 Hz), 8.73 (d, 4H, J = 8.1 Hz), 8.35 (s, 1H), 8.01 (d, 2H, J = 7.9 Hz), 7.91 (dd, 4H, J = 8.1 Hz), 7.69 (t, 1H, J = 7.8 Hz), 7.38 (dd, 4H, J = 5.3 Hz) p.p.m. EI—MS m/z 540 (100); C₃₆H₂₄N₆ requires 540.6. Analysis found: C 79.25, H 4.63, N 14.93%; C₃₆H₂₄N₆ requires: C 79.98, H 4.47, N 15.54%. Colourless plate-shaped crystals suitable for crystallography were obtained by slow evaporation of a solution in CH₂Cl₂.

S3. Refinement

The title compound, (I), crystallized in the orthorhombic system. The solvate was disordered over a twofold axis. All H atoms were assigned calculated positions [C—H = 0.95 and 0.99 Å in ligand molecule and the solvate, respectively] and included in the refinement in riding-motion approximation, with U_iso = 1.2U_eq of the carrier atom.

Computing details

Data collection: COLLECT (Nonius, 1997-2001); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. A view of (I), showing the atomic numbering scheme, with H atoms and the solvate molecule omitted, and displacement ellipsoids drawn at the 50% probability level.

1,3-di(2,2':6',2''-terpyridin-4'-yl)benzene dichloromethane solvate

Crystal data

C36H24N6·CH2Cl2	Dx = 1.388 Mg m^−3
Mr = 625.54	Melting point: > 300° C K
Orthorhombic, Pccn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2ac	Cell parameters from 3806 reflections
a = 8.0259 (16) Å	θ = 2.6–27.5°
b = 18.111 (4) Å	µ = 0.26 mm^−1
c = 20.590 (4) Å	T = 150 K
V = 2992.8 (10) Å^3	Plate, colorless
Z = 4	0.30 × 0.20 × 0.08 mm
F(000) = 1296

Data collection

Nonius KappaCCD diffractometer	1822 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.107
Graphite monochromator	θmax = 25.0°, θmin = 2.8°
Detector resolution: 9 pixels mm^-1	h = −9→9
ϕ scans and ω scans with κ offsets	k = −21→21
21389 measured reflections	l = −24→24
2639 independent reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.063	H-atom parameters constrained
wR(F^2) = 0.175	w = 1/[σ^2(Fo^2) + (0.0822P)^2 + 1.8351P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max < 0.001
2639 reflections	Δρmax = 0.29 e Å^−3
215 parameters	Δρmin = −0.51 e Å^−3
1 restraint	Extinction correction: SHELXTL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0055 (13)

Special details

Experimental. The cell parameters were calculated from all the data collected out to 27.5 ° but the refinement used data up to 25 ° as the higher angle data were not useful.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving least-squares planes.

Mean-plane data from final SHELXL refinement run:-

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

Plane 1: 6.6750 (0.0059) x − 2.7506 (0.0208) y + 10.9966 (0.0225) z = 7.1176 (0.0076)

* −0.0016 (0.0020) C15 * −0.0084 (0.0019) N3 * 0.0089 (0.0022) C19 * 0.0008 (0.0022) C18 * −0.0107 (0.0022) C17 * 0.0109 (0.0022) C16

Rms deviation of fitted atoms = 0.0080

Plane 2: 6.9083 (0.0051) x − 4.8034 (0.0191) y + 8.9458 (0.0217) z = 6.2108 (0.0093)

Angle to previous plane (with approximate e.s.d.) = 8.81 (0.15)

* −0.0045 (0.0019) C5 * 0.0059 (0.0019) C6 * −0.0005 (0.0019) C7 * −0.0067 (0.0019) C8 * 0.0085 (0.0019) C9 * −0.0029 (0.0018) N1

Rms deviation of fitted atoms = 0.0055

Plane 3: 6.7521 (0.0062) x − 7.0666 (0.0222) y + 7.7034 (0.0246) z = 5.5686 (0.0158)

Angle to previous plane (with approximate e.s.d.) = 8.04 (0.16)

* 0.0024 (0.0021) C10 * −0.0058 (0.0022) C11 * 0.0032 (0.0023) C12 * 0.0031 (0.0023) C13 * −0.0068 (0.0023) C14 * 0.0040 (0.0021) N2

Rms deviation of fitted atoms = 0.0045

Plane 4: 8.0246 (0.0016) x − 0.3219 (0.0313) y + 0.0264 (0.0126) z = 2.0964 (0.0094)

Angle to plane 2 (with approximate e.s.d.) = 30.02 (0.08)

* 0.0017 (0.0008) C1 * −0.0034 (0.0016) C2 * 0.0035 (0.0017) C3 * −0.0018 (0.0009) C4

Rms deviation of fitted atoms = 0.0028

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > 2σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
N1	0.2572 (3)	0.52182 (12)	0.50705 (11)	0.0340 (6)
N2	0.0243 (3)	0.41140 (15)	0.62080 (11)	0.0445 (7)
N3	0.4926 (3)	0.57951 (14)	0.36739 (11)	0.0413 (6)
C1	0.2500	0.2500	0.43452 (18)	0.0337 (9)
H1	0.2500	0.2500	0.4807	0.040*
C2	0.2522 (4)	0.31737 (16)	0.40198 (13)	0.0345 (7)
C3	0.2532 (4)	0.31655 (17)	0.33403 (13)	0.0394 (7)
H3A	0.2561	0.3617	0.3106	0.047*
C4	0.2500	0.2500	0.30102 (19)	0.0434 (11)
H4	0.2500	0.2500	0.2549	0.052*
C5	0.3287 (3)	0.51619 (16)	0.44867 (13)	0.0340 (7)
C6	0.3308 (4)	0.45097 (16)	0.41315 (13)	0.0341 (7)
H6A	0.3844	0.4492	0.3720	0.041*
C7	0.2540 (3)	0.38836 (15)	0.43813 (12)	0.0324 (6)
C8	0.1787 (4)	0.39460 (16)	0.49893 (13)	0.0355 (7)
H8A	0.1237	0.3533	0.5176	0.043*
C9	0.1843 (4)	0.46137 (16)	0.53214 (13)	0.0330 (7)
C10	0.1103 (4)	0.46891 (16)	0.59795 (13)	0.0355 (7)
C11	0.1353 (4)	0.53304 (18)	0.63385 (14)	0.0444 (8)
H11A	0.1960	0.5732	0.6160	0.053*
C12	0.0702 (4)	0.5373 (2)	0.69594 (15)	0.0503 (9)
H12A	0.0868	0.5802	0.7216	0.060*
C13	−0.0183 (4)	0.4788 (2)	0.71989 (15)	0.0500 (9)
H13A	−0.0642	0.4804	0.7624	0.060*
C14	−0.0396 (4)	0.4177 (2)	0.68122 (15)	0.0531 (9)
H14A	−0.1029	0.3776	0.6979	0.064*
C15	0.4048 (3)	0.58530 (16)	0.42270 (13)	0.0343 (7)
C16	0.3818 (4)	0.65213 (17)	0.45456 (15)	0.0442 (8)
H16A	0.3210	0.6543	0.4941	0.053*
C17	0.4490 (4)	0.71555 (18)	0.42764 (16)	0.0471 (8)
H17A	0.4316	0.7621	0.4478	0.057*
C18	0.5403 (4)	0.71052 (19)	0.37203 (16)	0.0473 (8)
H18A	0.5893	0.7532	0.3532	0.057*
C19	0.5600 (4)	0.64198 (18)	0.34366 (15)	0.0471 (8)
H19A	0.6249	0.6387	0.3052	0.057*
Cl1	0.2500	0.7500	0.23315 (7)	0.1056 (7)
Cl2	0.3349 (3)	0.75024 (13)	0.10018 (9)	0.0715 (6)	0.50
C1S	0.1658 (9)	0.7377 (5)	0.15429 (13)	0.067 (2)	0.50
H1S	0.1181	0.6876	0.1496	0.080*	0.50
H2S	0.0773	0.7745	0.1457	0.080*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0385 (13)	0.0286 (14)	0.0351 (12)	0.0003 (11)	−0.0040 (11)	−0.0011 (10)
N2	0.0506 (16)	0.0447 (17)	0.0382 (14)	0.0000 (13)	0.0054 (12)	−0.0028 (12)
N3	0.0476 (15)	0.0374 (15)	0.0389 (13)	−0.0066 (12)	0.0002 (11)	0.0019 (11)
C1	0.042 (2)	0.032 (2)	0.0275 (18)	−0.0018 (18)	0.000	0.000
C2	0.0387 (15)	0.0317 (17)	0.0332 (14)	−0.0007 (13)	0.0000 (13)	0.0005 (12)
C3	0.0533 (18)	0.0331 (17)	0.0318 (14)	0.0020 (14)	0.0018 (14)	0.0037 (13)
C4	0.067 (3)	0.035 (3)	0.028 (2)	0.005 (2)	0.000	0.000
C5	0.0352 (15)	0.0325 (17)	0.0341 (14)	0.0022 (12)	−0.0044 (12)	0.0001 (12)
C6	0.0381 (15)	0.0303 (16)	0.0340 (14)	0.0012 (12)	0.0003 (12)	0.0007 (12)
C7	0.0382 (15)	0.0277 (15)	0.0312 (13)	0.0035 (12)	−0.0048 (13)	0.0009 (12)
C8	0.0393 (15)	0.0322 (16)	0.0349 (14)	−0.0010 (13)	−0.0014 (13)	0.0044 (13)
C9	0.0359 (15)	0.0290 (17)	0.0341 (14)	0.0014 (12)	−0.0040 (12)	0.0003 (12)
C10	0.0367 (15)	0.0343 (17)	0.0354 (15)	0.0043 (13)	−0.0035 (13)	−0.0002 (13)
C11	0.0501 (19)	0.0415 (19)	0.0416 (16)	0.0005 (15)	0.0044 (14)	−0.0058 (14)
C12	0.052 (2)	0.056 (2)	0.0421 (17)	0.0042 (17)	−0.0013 (15)	−0.0151 (16)
C13	0.053 (2)	0.062 (2)	0.0350 (16)	0.0123 (17)	0.0066 (14)	−0.0028 (15)
C14	0.057 (2)	0.059 (2)	0.0437 (18)	−0.0006 (17)	0.0108 (16)	0.0049 (16)
C15	0.0344 (15)	0.0301 (16)	0.0385 (15)	−0.0023 (12)	−0.0083 (12)	0.0015 (12)
C16	0.0495 (18)	0.0353 (19)	0.0480 (17)	−0.0039 (14)	−0.0001 (15)	−0.0042 (14)
C17	0.0512 (19)	0.0286 (17)	0.061 (2)	−0.0054 (14)	−0.0040 (16)	−0.0060 (15)
C18	0.0479 (18)	0.0365 (19)	0.0576 (19)	−0.0119 (15)	−0.0076 (16)	0.0109 (16)
C19	0.054 (2)	0.044 (2)	0.0430 (17)	−0.0090 (16)	−0.0003 (15)	0.0049 (15)
Cl1	0.173 (2)	0.0918 (14)	0.0523 (9)	−0.0096 (13)	0.000	0.000
Cl2	0.0750 (12)	0.0853 (16)	0.0542 (10)	−0.0136 (12)	0.0105 (9)	0.0017 (11)
C1S	0.055 (4)	0.077 (6)	0.068 (5)	0.001 (4)	0.011 (4)	0.001 (4)

Geometric parameters (Å, º)

N1—C5	1.336 (4)	C10—C11	1.391 (4)
N1—C9	1.344 (4)	C11—C12	1.383 (4)
N2—C10	1.335 (4)	C11—H11A	0.9500
N2—C14	1.351 (4)	C12—C13	1.367 (5)
N3—C15	1.343 (4)	C12—H12A	0.9500
N3—C19	1.346 (4)	C13—C14	1.374 (5)
C1—C2	1.392 (3)	C13—H13A	0.9500
C1—H1	0.9500	C14—H14A	0.9500
C2—C3	1.399 (4)	C15—C16	1.389 (4)
C2—C7	1.486 (4)	C16—C17	1.385 (4)
C3—C4	1.384 (3)	C16—H16A	0.9500
C3—H3A	0.9500	C17—C18	1.363 (5)
C4—C3^i	1.384 (3)	C17—H17A	0.9500
C4—H4	0.9500	C18—C19	1.381 (5)
C5—C6	1.389 (4)	C18—H18A	0.9500
C5—C15	1.492 (4)	C19—H19A	0.9500
C6—C7	1.389 (4)	Cl1—C1S	1.773 (5)
C6—H6A	0.9500	Cl1—C1S^ii	1.773 (5)
C7—C8	1.395 (4)	Cl2—C1S	1.770 (5)
C8—C9	1.390 (4)	C1S—H1S	0.9900
C8—H8A	0.9500	C1S—H2S	0.9900
C9—C10	1.486 (4)
C5—N1—C9	118.1 (2)	C10—C11—H11A	120.6
C10—N2—C14	117.1 (3)	C13—C12—C11	119.1 (3)
C15—N3—C19	116.9 (3)	C13—C12—H12A	120.4
C2^i—C1—C2	122.5 (3)	C11—C12—H12A	120.4
C2—C1—H1	118.8	C12—C13—C14	118.7 (3)
C1—C2—C3	118.2 (3)	C12—C13—H13A	120.7
C1—C2—C7	121.2 (2)	C14—C13—H13A	120.7
C3—C2—C7	120.7 (3)	N2—C14—C13	123.7 (3)
C4—C3—C2	120.0 (3)	N2—C14—H14A	118.2
C4—C3—H3A	120.0	C13—C14—H14A	118.2
C2—C3—H3A	120.0	N3—C15—C16	122.6 (3)
C3—C4—C3^i	121.2 (4)	N3—C15—C5	116.9 (2)
C3—C4—H4	119.4	C16—C15—C5	120.5 (3)
N1—C5—C6	122.9 (3)	C17—C16—C15	118.8 (3)
N1—C5—C15	115.7 (2)	C17—C16—H16A	120.6
C6—C5—C15	121.3 (2)	C15—C16—H16A	120.6
C5—C6—C7	119.6 (3)	C18—C17—C16	119.4 (3)
C5—C6—H6A	120.2	C18—C17—H17A	120.3
C7—C6—H6A	120.2	C16—C17—H17A	120.3
C6—C7—C8	117.3 (3)	C17—C18—C19	118.5 (3)
C6—C7—C2	121.7 (2)	C17—C18—H18A	120.7
C8—C7—C2	121.0 (3)	C19—C18—H18A	120.7
C9—C8—C7	119.9 (3)	N3—C19—C18	123.8 (3)
C9—C8—H8A	120.1	N3—C19—H19A	118.1
C7—C8—H8A	120.1	C18—C19—H19A	118.1
N1—C9—C8	122.3 (3)	C1S—Cl1—C1S^ii	47.3 (4)
N1—C9—C10	116.7 (3)	Cl2—C1S—Cl1	105.6 (4)
C8—C9—C10	121.0 (3)	Cl2—C1S—H1S	110.6
N2—C10—C11	122.6 (3)	Cl1—C1S—H1S	110.6
N2—C10—C9	117.1 (3)	Cl2—C1S—H2S	110.6
C11—C10—C9	120.3 (3)	Cl1—C1S—H2S	110.6
C12—C11—C10	118.9 (3)	H1S—C1S—H2S	108.8
C12—C11—H11A	120.6
C2^i—C1—C2—C3	−0.4 (4)	N1—C9—C10—N2	173.9 (3)
C2^i—C1—C2—C7	179.8 (3)	C8—C9—C10—N2	−6.5 (4)
C1—C2—C3—C4	0.8 (4)	N1—C9—C10—C11	−7.7 (4)
C7—C2—C3—C4	−179.4 (2)	C8—C9—C10—C11	171.8 (3)
C2—C3—C4—C3^i	−0.4 (2)	N2—C10—C11—C12	0.7 (5)
C9—N1—C5—C6	0.0 (4)	C9—C10—C11—C12	−177.5 (3)
C9—N1—C5—C15	178.9 (2)	C10—C11—C12—C13	−0.8 (5)
N1—C5—C6—C7	0.9 (4)	C11—C12—C13—C14	0.0 (5)
C15—C5—C6—C7	−178.0 (3)	C10—N2—C14—C13	−1.1 (5)
C5—C6—C7—C8	−0.5 (4)	C12—C13—C14—N2	1.0 (5)
C5—C6—C7—C2	179.7 (3)	C19—N3—C15—C16	0.5 (4)
C1—C2—C7—C6	149.5 (2)	C19—N3—C15—C5	179.4 (3)
C3—C2—C7—C6	−30.3 (4)	N1—C5—C15—N3	173.2 (2)
C1—C2—C7—C8	−30.3 (4)	C6—C5—C15—N3	−7.8 (4)
C3—C2—C7—C8	150.0 (3)	N1—C5—C15—C16	−7.9 (4)
C6—C7—C8—C9	−0.7 (4)	C6—C5—C15—C16	171.1 (3)
C2—C7—C8—C9	179.1 (3)	N3—C15—C16—C17	1.3 (5)
C5—N1—C9—C8	−1.2 (4)	C5—C15—C16—C17	−177.5 (3)
C5—N1—C9—C10	178.3 (2)	C15—C16—C17—C18	−2.2 (5)
C7—C8—C9—N1	1.6 (4)	C16—C17—C18—C19	1.2 (5)
C7—C8—C9—C10	−177.9 (3)	C15—N3—C19—C18	−1.6 (5)
C14—N2—C10—C11	0.2 (4)	C17—C18—C19—N3	0.7 (5)
C14—N2—C10—C9	178.5 (3)	C1S^ii—Cl1—C1S—Cl2	7.0 (3)

Symmetry codes: (i) −x+1/2, −y+1/2, z; (ii) −x+1/2, −y+3/2, z.