A co-crystal of 1,10-phenanthroline with boric acid: a novel aza-aromatic complex

The title compound, C₁₂H₈N₂·2B(OH)₃, is best described as a host–guest complex in which the B(OH)₃ mol­ecules form a hydrogen-bonded cyclic network of layers parallel to the ab plane into which the 1,10-phenanthroline mol­ecules are bound. An extensive network of hydrogen bonds are responsible for the crystal stability. No π-stacking inter­actions occur between the 1,10-phenanthroline mol­ecules.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.036
• wR factor = 0.096
• Data-to-parameter ratio = 13.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT906_ALERT_3_C Large K value in the Analysis of Variance ......      2.305
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          5

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ? Do !
PLAT007_ALERT_5_G Note: Number of Unrefined Donor-H Atoms ........          6

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   2 ALERT level G = General information/check it is not something unexpected

   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
   2 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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S1. Comment

The design and synthesis of novel systems of noncovalent hosts involving hydrogen bonds is a vast research area in both molecular and supermolecular chemistry, see Pedireddi et al. (1997). In the field of supermolecular synthesis, recognition between the complementary functional groups is a main factor for the evaluation of influence of noncovalent interaction in the formation of specific architecture, see: Lehn (1990). In recent times, boric acid derivatives have been well considered to be potential co-crystal formers. In fact, the ability of –B(OH)₂ functionality to form a variety of hydrogen bonds through different conformations makes it a very suitable moiety for the synthesis of novel molecular complexes, see Lee et al. (2005). The –B(OH)₂ moiety is known to have an affinity for pyridyl N-atoms, often forming O—H···N hydrogen bonds, as observed in some crystals of boronic acids with aza compounds,see Talwelkar & Pedireddi (2010).

Non-covalent hosts are generally designed and synthesized by employing appropriate functional groups at required symmetry positions to form a cyclic network through the hydrogen bonds, see Pedireddi (2001). This effect has been observed vividly in simple molecular adduct such as 1,10-phenanthroline and water, see Tian et al. (1995). In this complex, a water molecule interacts with a molecule of 1,10-phenanthroline through O–H···N hydrogen bonds and an unique aza-aromatic complex is formed. In the latter, 1,10-phenanthroline could be considered as a host. Herein, we report the crystal structure of boric acid with 1,10-phenanthroline as an aza-donor compound.

As seen in Figure 1, the phen molecule forms a H-bonded adduct via two B–O–H···N interacts from one of the included B(OH)₃ moieties. A strong network of hydrogen bonds among the B(OH)₃ units forms a layered structure with alternating B(OH)₃ and phen layers that reside in the ab planes (Figure 2). The B(OH)₃ layers alone can be described as a cyclic network formed by hydrogen bonding interactions as can be seen in Figure 3. There are not any significant π-stacking interactions between the phen molecules.

Related literature

For the design and synthesis of novel systems of non-covalent hosts involving hydrogen bonds, see: Pedireddi et al. (1997). In the field of supermolecular synthesis, recognition between the complementary functional groups is a main factor for the evaluation of influence of noncovalent interactions in the formation of specific architecture, see: Lehn (1990). The ability of the –B(OH)₂ functionality to form a variety of hydrogen bonds through different conformations makes it a very suitable moiety for the synthesis of novel molecular complexes, see: Lee et al. (2005). It is known to have an affinity for pyridyl N atoms, often forming O—H···N hydrogen bonds, as observed in some crystals of boronic acids with aza compounds (Talwelkar & Pedireddi, 2010). Non-covalent hosts are generally designed and synthesized by employing appropriate functional groups at required symmetry positions to form a cyclic network through the hydrogen bonds, see: Pedireddi (2001). This effect has been observed vividly in simple molecular adducts such as 1,10-phenanthroline and water (Tian et al., 1995).

S2. Experimental

(CH₃)₃NBH₃ (0.73 g, 10 mmol) and iodine (2.54 g, 5 mmol) were dissolved in toluene (4 ml) and stirred for 30 min. A solution of 1,10-phenanthroline (1.98 g, 10 mmol) in toluene (4 ml) was added, and the mixture refluxed overnight. The solution was cooled to room temperature, during which process orange-brown crystals were formed. The product was recrystallized twice from CH₃CN to obtain analytically pure, red-brown crystalline product.

¹H NMR (DMSO-d₆, 300 MHz): δ_H 9.22 (dd, J = 2.8, 1.6 Hz, 2H), 8.67 (dd, J = 6.3, 1.6 Hz, 2H), 8.14 (s, 2H), 7.93 (q, J = 4.4 Hz, 2H), 6.62 (br, 2H); ¹³C NMR (DMSO-d₆, 100 MHz): δ_C 151.67, 146.27, 139.09, 130.58, 128.77, 125.66.

S3. Refinement

H-atoms were placed in calculated positions and allowed to ride during subsequent refinement, with U_iso(H) = 1.2U_eq(C) and C—H distances of 0.93 Å for the aromatic H atoms and with U_iso(H) = 1.5U_eq(C) and O—H distances of 0.85 Å for hydroxyl H atoms.

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2011); cell refinement: CrysAlis PRO (Oxford Diffraction, 2011); data reduction: CrysAlis PRO (Oxford Diffraction, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. The molecular structure of I, with the atom-numbering scheme. Displacement ellipsoids for non-hydrogen atoms are drawn at the 50% probability level.
	Fig. 2. A packing diagram of I viewed along the b axis.
	Fig. 3. A representation of the two-dimensional B(OH)3 layers formed via hydrogen bonding in the structure of I.

Boric acid–1,10-phenanthroline (2/1)

Crystal data

C12H8N2·2BH3O3	Z = 2
Mr = 303.87	F(000) = 316
Triclinic, P1	Dx = 1.435 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.1390 (13) Å	Cell parameters from 3335 reflections
b = 9.6189 (13) Å	θ = 3.2–25.3°
c = 10.4756 (15) Å	µ = 0.11 mm^−1
α = 93.767 (11)°	T = 295 K
β = 101.546 (14)°	Prism, brown
γ = 90.644 (13)°	0.35 × 0.16 × 0.09 mm
V = 703.05 (19) Å^3

Data collection

Oxford Diffraction Xcalibur Eos diffractometer	2580 independent reflections
Radiation source: fine-focus sealed tube	1972 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
Detector resolution: 16.0514 pixels mm^-1	θmax = 25.4°, θmin = 3.2°
ω scans	h = −8→8
Absorption correction: multi-scan [CrysAlis PRO (Oxford Diffraction, 2011) based on Clark & Reid (1995)]	k = −11→11
Tmin = 0.956, Tmax = 1.000	l = −12→12
10473 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.036	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.096	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.044P)^2 + 0.1204P] where P = (Fo^2 + 2Fc^2)/3
2580 reflections	(Δ/σ)max < 0.001
199 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.13 e Å^−3

Special details

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 l.s. planes.

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
B1	0.0170 (3)	0.65229 (18)	0.64598 (18)	0.0421 (4)
B2	0.2786 (3)	−0.00132 (19)	0.59856 (18)	0.0439 (4)
C1	0.1542 (2)	0.83587 (17)	1.04155 (17)	0.0488 (4)
H1A	0.1058	0.9001	0.9816	0.059*
C2	0.1999 (3)	0.8822 (2)	1.17305 (19)	0.0573 (5)
H2A	0.1815	0.9743	1.1999	0.069*
C3	0.2718 (3)	0.7893 (2)	1.26068 (18)	0.0574 (5)
H3A	0.3014	0.8168	1.3493	0.069*
C4	0.3018 (2)	0.65145 (18)	1.21789 (15)	0.0464 (4)
C5	0.2496 (2)	0.61314 (16)	1.08273 (14)	0.0369 (4)
C6	0.3852 (3)	0.5520 (2)	1.30610 (17)	0.0587 (5)
H6A	0.4195	0.5784	1.3948	0.070*
C7	0.4149 (3)	0.4217 (2)	1.26368 (18)	0.0567 (5)
H7	0.4714	0.3593	1.3231	0.068*
C8	0.3612 (2)	0.37654 (17)	1.12795 (16)	0.0434 (4)
C9	0.2778 (2)	0.47095 (15)	1.03670 (14)	0.0361 (3)
C10	0.3890 (2)	0.23972 (17)	1.08186 (18)	0.0521 (5)
H10	0.4451	0.1755	1.1396	0.062*
C11	0.3337 (2)	0.20134 (17)	0.95254 (18)	0.0513 (4)
H11	0.3496	0.1107	0.9206	0.062*
C12	0.2522 (2)	0.30118 (16)	0.86861 (16)	0.0449 (4)
H12	0.2150	0.2741	0.7802	0.054*
N1	0.17492 (17)	0.70652 (13)	0.99611 (12)	0.0403 (3)
N2	0.22495 (17)	0.43158 (12)	0.90711 (12)	0.0385 (3)
O1	0.07961 (17)	0.52138 (11)	0.66548 (10)	0.0515 (3)
H1	0.1261	0.5050	0.7441	0.077*
O2	0.02929 (18)	0.75343 (11)	0.74334 (11)	0.0548 (3)
H2	0.0796	0.7268	0.8180	0.082*
O3	−0.06394 (19)	0.68679 (11)	0.52361 (11)	0.0583 (4)
H3	−0.0642	0.6217	0.4646	0.087*
O4	0.31472 (16)	0.10158 (11)	0.52210 (12)	0.0539 (3)
H4	0.2251	0.1595	0.5081	0.081*
O5	0.39825 (18)	−0.11040 (12)	0.61562 (12)	0.0587 (3)
H5	0.4881	−0.1068	0.5734	0.088*
O6	0.12843 (18)	0.00858 (12)	0.65864 (12)	0.0584 (3)
H6	0.1101	−0.0702	0.6871	0.088*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
B1	0.0496 (11)	0.0403 (10)	0.0372 (10)	0.0098 (8)	0.0080 (8)	0.0079 (8)
B2	0.0530 (12)	0.0390 (10)	0.0376 (10)	0.0063 (8)	0.0042 (9)	0.0014 (8)
C1	0.0501 (10)	0.0455 (10)	0.0492 (10)	0.0076 (7)	0.0074 (8)	−0.0006 (8)
C2	0.0585 (11)	0.0549 (11)	0.0557 (11)	0.0042 (9)	0.0099 (9)	−0.0129 (9)
C3	0.0567 (11)	0.0713 (13)	0.0406 (10)	−0.0023 (9)	0.0063 (8)	−0.0125 (9)
C4	0.0398 (9)	0.0612 (11)	0.0362 (9)	−0.0027 (8)	0.0036 (7)	0.0018 (8)
C5	0.0307 (8)	0.0468 (9)	0.0328 (8)	−0.0008 (6)	0.0049 (6)	0.0055 (7)
C6	0.0639 (12)	0.0747 (13)	0.0333 (9)	−0.0030 (10)	−0.0013 (8)	0.0078 (9)
C7	0.0568 (11)	0.0685 (13)	0.0422 (10)	0.0011 (9)	−0.0019 (8)	0.0214 (9)
C8	0.0355 (9)	0.0518 (10)	0.0430 (9)	−0.0009 (7)	0.0045 (7)	0.0144 (7)
C9	0.0301 (8)	0.0432 (9)	0.0354 (8)	−0.0011 (6)	0.0056 (6)	0.0091 (7)
C10	0.0482 (10)	0.0480 (10)	0.0603 (12)	0.0058 (8)	0.0051 (9)	0.0234 (9)
C11	0.0540 (10)	0.0400 (9)	0.0611 (12)	0.0059 (7)	0.0121 (9)	0.0102 (8)
C12	0.0496 (10)	0.0401 (9)	0.0447 (9)	0.0034 (7)	0.0080 (8)	0.0046 (7)
N1	0.0409 (7)	0.0419 (7)	0.0380 (7)	0.0046 (6)	0.0071 (6)	0.0032 (6)
N2	0.0397 (7)	0.0395 (7)	0.0362 (7)	0.0021 (5)	0.0062 (6)	0.0064 (6)
O1	0.0702 (8)	0.0450 (6)	0.0346 (6)	0.0199 (5)	−0.0025 (5)	0.0063 (5)
O2	0.0850 (9)	0.0415 (6)	0.0373 (6)	0.0096 (6)	0.0093 (6)	0.0062 (5)
O3	0.0905 (9)	0.0455 (7)	0.0360 (6)	0.0270 (6)	0.0032 (6)	0.0077 (5)
O4	0.0538 (7)	0.0472 (7)	0.0644 (8)	0.0162 (5)	0.0151 (6)	0.0198 (6)
O5	0.0678 (8)	0.0517 (7)	0.0620 (8)	0.0202 (6)	0.0188 (6)	0.0226 (6)
O6	0.0742 (9)	0.0463 (7)	0.0606 (8)	0.0099 (6)	0.0266 (7)	0.0060 (6)

Geometric parameters (Å, º)

B1—O2	1.351 (2)	C6—H6A	0.9300
B1—O1	1.355 (2)	C7—C8	1.433 (2)
B1—O3	1.361 (2)	C7—H7	0.9300
B2—O6	1.349 (2)	C8—C10	1.402 (2)
B2—O5	1.359 (2)	C8—C9	1.411 (2)
B2—O4	1.367 (2)	C9—N2	1.3612 (19)
C1—N1	1.323 (2)	C10—C11	1.358 (2)
C1—C2	1.393 (2)	C10—H10	0.9300
C1—H1A	0.9300	C11—C12	1.397 (2)
C2—C3	1.355 (3)	C11—H11	0.9300
C2—H2A	0.9300	C12—N2	1.3207 (19)
C3—C4	1.404 (2)	C12—H12	0.9300
C3—H3A	0.9300	O1—H1	0.8500
C4—C5	1.413 (2)	O2—H2	0.8501
C4—C6	1.425 (2)	O3—H3	0.8500
C5—N1	1.3559 (19)	O4—H4	0.8501
C5—C9	1.450 (2)	O5—H5	0.8501
C6—C7	1.336 (3)	O6—H6	0.8501
O2—B1—O1	123.27 (15)	C6—C7—H7	119.5
O2—B1—O3	116.79 (14)	C8—C7—H7	119.5
O1—B1—O3	119.94 (15)	C10—C8—C9	118.24 (15)
O6—B2—O5	121.00 (16)	C10—C8—C7	121.84 (15)
O6—B2—O4	119.75 (15)	C9—C8—C7	119.92 (16)
O5—B2—O4	119.23 (17)	N2—C9—C8	121.47 (14)
N1—C1—C2	124.43 (17)	N2—C9—C5	119.64 (13)
N1—C1—H1A	117.8	C8—C9—C5	118.88 (14)
C2—C1—H1A	117.8	C11—C10—C8	119.70 (15)
C3—C2—C1	118.03 (16)	C11—C10—H10	120.2
C3—C2—H2A	121.0	C8—C10—H10	120.2
C1—C2—H2A	121.0	C10—C11—C12	118.49 (16)
C2—C3—C4	120.11 (16)	C10—C11—H11	120.8
C2—C3—H3A	119.9	C12—C11—H11	120.8
C4—C3—H3A	119.9	N2—C12—C11	124.05 (15)
C3—C4—C5	118.01 (16)	N2—C12—H12	118.0
C3—C4—C6	121.94 (16)	C11—C12—H12	118.0
C5—C4—C6	120.05 (16)	C1—N1—C5	118.04 (13)
N1—C5—C4	121.35 (14)	C12—N2—C9	118.04 (13)
N1—C5—C9	119.78 (13)	B1—O1—H1	115.9
C4—C5—C9	118.86 (14)	B1—O2—H2	113.4
C7—C6—C4	121.23 (16)	B1—O3—H3	114.0
C7—C6—H6A	119.4	B2—O4—H4	113.0
C4—C6—H6A	119.4	B2—O5—H5	113.6
C6—C7—C8	121.04 (16)	B2—O6—H6	108.1

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N2	0.85	1.90	2.7360 (16)	168.9
O2—H2···N1	0.85	1.88	2.7132 (17)	167.4
O3—H3···O1^i	0.85	1.86	2.7076 (15)	176.8
O4—H4···O3^i	0.85	1.89	2.7286 (16)	169.1
O5—H5···O4^ii	0.85	1.89	2.7355 (18)	179.0
O6—H6···O2^iii	0.85	1.95	2.7946 (17)	171.8

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