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As part of an effort to design more efficient dyes for dye-sensitized solar cells (DSCs), structure–property relationships are established in the world's best-performing chemical series of dyes: 2,2′-bipyridyl-4,4′-carboxylatoruthenium(II) complexes. Statistical analysis, based on crystallographic data from the Cambridge Structural Database, is used to determine common structural features and the effects of structural change to its salient molecular constituents. Also included is the report of two new crystal structures for tris(2,2′-bipyridyl)dichlororuthenium(II)hexahydrate and tris(2,2′-bipyridyl)iron(II)dithiocyanate; these add to this statistical enquiry. Results show that the metal (M) core exhibits a distorted octahedral environment with M—N π-backbonding effects affording the propensity of the metal ion towards oxidation. The same characteristics are observed in iron-based analogues. The role of carboxylic groups in this series of dyes is assessed by comparing complexes which contain or are devoid of COOH groups. Space-group variation and large molecular conformational differences occur when COOH groups are present, while such structural features are very similar in their absence. The nature of the anion is also shown to influence the structure of COOH-containing complexes. These structural findings are corroborated by solution-based UV–vis absorption spectroscopy and DSC device performance tests. The presence of COOH groups in this series of compounds is shown to be mandatory for dye-uptake in TiO2 in the DSC fabrication process. Throughout this study, results are compared with those of the world's most famous DSC dye, N3 (N719 in its fully protonated form): cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II). Overall, the molecular origins of charge-transfer in these complexes are ascertained. The findings have important implications to the materials discovery of more efficient dyes for DSC technology.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768112009263/zb5022sup1.cif
Contains datablocks I, II, global

fcf

Structure factor file (CIF format) https://doi.org/10.1107/S0108768112009263/zb5022Isup2.fcf
Contains datablock I

fcf

Structure factor file (CIF format) https://doi.org/10.1107/S0108768112009263/zb5022IIsup3.fcf
Contains datablock II

CCDC references: 879418; 879419

Computing details top

For both compounds, data collection: CrystalClear (Rigaku Inc., 2008); cell refinement: CrystalClear (Rigaku Inc., 2008); data reduction: CrystalClear (Rigaku Inc., 2008). Program(s) used to solve structure: SHELXS97 (Sheldrick, 2008) for (I); SIR92 (Altomare et al., J. Appl. Cryst. (1994). 27, 435) for (II). For both compounds, program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999).

Figures top
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(I) Tris(2,2?-bipyridyl)dichlororuthenium(II) hexahydrate top
Crystal data top
C30H24N6RuCl2·6(H2O)Dx = 1.584 Mg m3
Mr = 748.62Mo Kα radiation, λ = 0.71073 Å
Hexagonal, P6/mccCell parameters from 3247 reflections
a = 13.1383 (12) Åθ = 5.3–55.0°
c = 20.995 (3) ŵ = 0.72 mm1
V = 3138.6 (6) Å3T = 150 K
Z = 4Chip, red
F(000) = 15360.21 × 0.16 × 0.12 mm
Data collection top
Rigaku Saturn724+ (2x2 bin mode)
diffractometer
1220 independent reflections
Radiation source: fine-focus sealed tube994 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.086
Detector resolution: 10 pixels mm-1θmax = 27.5°, θmin = 3.7°
phi or ω oscillation scansh = 717
Absorption correction: empirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
k = 177
Tmin = 0.676, Tmax = 1.000l = 2426
11174 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.061Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.153H-atom parameters constrained
S = 1.09 w = 1/[σ2(Fo2) + (0.0767P)2 + 5.4397P]
where P = (Fo2 + 2Fc2)/3
1220 reflections(Δ/σ)max < 0.001
57 parametersΔρmax = 0.98 e Å3
0 restraintsΔρmin = 0.56 e Å3
Crystal data top
C30H24N6RuCl2·6(H2O)Z = 4
Mr = 748.62Mo Kα radiation
Hexagonal, P6/mccµ = 0.72 mm1
a = 13.1383 (12) ÅT = 150 K
c = 20.995 (3) Å0.21 × 0.16 × 0.12 mm
V = 3138.6 (6) Å3
Data collection top
Rigaku Saturn724+ (2x2 bin mode)
diffractometer
1220 independent reflections
Absorption correction: empirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
994 reflections with I > 2σ(I)
Tmin = 0.676, Tmax = 1.000Rint = 0.086
11174 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0610 restraints
wR(F2) = 0.153H-atom parameters constrained
S = 1.09Δρmax = 0.98 e Å3
1220 reflectionsΔρmin = 0.56 e Å3
57 parameters
Special details top

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

Refinement. Loop_ _platon_squeeze_void_nr _platon_squeeze_void_average_x _platon_squeeze_void_average_y _platon_squeeze_void_average_z _platon_squeeze_void_volume _platon_squeeze_void_count_electrons _platon_squeeze_void_content 1 − 0.010 − 0.009 − 0.103 930 363 ' ' 2 0.000 0.500 0.250 7 0 ' ' 3 0.000 0.500 0.750 7 0 ' ' 4 0.500 0.000 0.250 7 0 ' ' 5 0.500 0.000 0.750 7 0 ' ' 6 0.500 0.500 0.250 7 0 ' ' 7 0.500 0.500 0.750 7 0 ' '

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.6811 (3)0.2077 (3)0.19802 (16)0.0292 (8)
C10.7618 (3)0.1800 (3)0.2205 (2)0.0287 (8)
C20.7861 (4)0.1029 (4)0.1872 (2)0.0372 (10)
H20.84090.08430.20300.045*
C50.6271 (4)0.1597 (4)0.1426 (2)0.0320 (9)
H50.57220.17830.12710.038*
C30.7288 (4)0.0542 (4)0.1308 (2)0.0370 (10)
H30.74360.00170.10870.044*
C40.6494 (4)0.0841 (4)0.1076 (2)0.0370 (10)
H40.61150.05400.06890.044*
Ru10.66670.33330.25000.0243 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0276 (17)0.0239 (16)0.0355 (19)0.0124 (14)0.0038 (14)0.0001 (14)
C10.0284 (19)0.0230 (17)0.035 (2)0.0134 (15)0.0049 (16)0.0037 (15)
C20.037 (2)0.030 (2)0.049 (3)0.020 (2)0.002 (2)0.0011 (19)
C50.030 (2)0.030 (2)0.032 (2)0.0130 (18)0.0009 (17)0.0014 (16)
C30.042 (2)0.027 (2)0.045 (2)0.020 (2)0.010 (2)0.0002 (19)
C40.036 (2)0.0253 (19)0.046 (3)0.0122 (17)0.0013 (19)0.0021 (18)
Ru10.0212 (3)0.0212 (3)0.0307 (5)0.01058 (15)0.0000.000
Geometric parameters (Å, º) top
N1—C51.345 (5)C3—C41.374 (6)
N1—C11.366 (5)C3—H30.9300
N1—Ru12.065 (3)C4—H40.9300
C1—C21.393 (6)Ru1—N1i2.065 (3)
C1—C1i1.454 (9)Ru1—N1ii2.065 (3)
C2—C31.376 (7)Ru1—N1iii2.065 (3)
C2—H20.9300Ru1—N1iv2.065 (3)
C5—C41.379 (6)Ru1—N1v2.065 (3)
C5—H50.9300
C5—N1—C1118.2 (3)C5—C4—H4120.6
C5—N1—Ru1126.5 (3)N1—Ru1—N1i78.98 (19)
C1—N1—Ru1115.1 (3)N1—Ru1—N1ii94.66 (13)
N1—C1—C2120.7 (4)N1i—Ru1—N1ii92.37 (18)
N1—C1—C1i115.4 (2)N1—Ru1—N1iii92.37 (18)
C2—C1—C1i124.0 (3)N1i—Ru1—N1iii94.66 (13)
C3—C2—C1119.9 (4)N1ii—Ru1—N1iii170.89 (18)
C3—C2—H2120.0N1—Ru1—N1iv94.66 (13)
C1—C2—H2120.0N1i—Ru1—N1iv170.89 (18)
N1—C5—C4123.2 (4)N1ii—Ru1—N1iv94.66 (13)
N1—C5—H5118.4N1iii—Ru1—N1iv78.98 (19)
C4—C5—H5118.4N1—Ru1—N1v170.89 (18)
C4—C3—C2119.3 (4)N1i—Ru1—N1v94.66 (13)
C4—C3—H3120.3N1ii—Ru1—N1v78.98 (19)
C2—C3—H3120.3N1iii—Ru1—N1v94.66 (13)
C3—C4—C5118.7 (4)N1iv—Ru1—N1v92.37 (18)
C3—C4—H4120.6
Symmetry codes: (i) y+1, x+1, z+1/2; (ii) y+1, xy, z; (iii) x+y+1, y, z+1/2; (iv) x+y+1, x+1, z; (v) x, xy, z+1/2.
(II) tris(2,2'-bipyridyl) iron(II) dithiocyanate top
Crystal data top
C30H24FeN6·2(NCS)Dx = 1.213 Mg m3
Mr = 642.28Mo Kα radiation, λ = 0.71075 Å
Hexagonal, P6/mccCell parameters from 3247 reflections
a = 13.1837 (9) Åθ = 5.3–55.0°
c = 21.2735 (14) ŵ = 0.20 mm1
V = 3202.2 (4) Å3T = 150 K
Z = 4Chip, red
F(000) = 12160.18 × 0.12 × 0.10 mm
Data collection top
Rigaku Saturn724+ (2x2 bin mode)
diffractometer
1259 independent reflections
Radiation source: fine-focus sealed tube1165 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.043
Detector resolution: 10 pixels mm-1θmax = 27.5°, θmin = 3.6°
phi or ω oscillation scansh = 1717
Absorption correction: empirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
k = 1617
Tmin = 0.857, Tmax = 1.000l = 2725
26491 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.049Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.115H-atom parameters constrained
S = 1.13 w = 1/[σ2(Fo2) + (0.0452P)2 + 3.3496P]
where P = (Fo2 + 2Fc2)/3
1259 reflections(Δ/σ)max < 0.001
57 parametersΔρmax = 0.32 e Å3
0 restraintsΔρmin = 0.27 e Å3
Crystal data top
C30H24FeN6·2(NCS)Z = 4
Mr = 642.28Mo Kα radiation
Hexagonal, P6/mccµ = 0.20 mm1
a = 13.1837 (9) ÅT = 150 K
c = 21.2735 (14) Å0.18 × 0.12 × 0.10 mm
V = 3202.2 (4) Å3
Data collection top
Rigaku Saturn724+ (2x2 bin mode)
diffractometer
1259 independent reflections
Absorption correction: empirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
1165 reflections with I > 2σ(I)
Tmin = 0.857, Tmax = 1.000Rint = 0.043
26491 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0490 restraints
wR(F2) = 0.115H-atom parameters constrained
S = 1.13Δρmax = 0.32 e Å3
1259 reflectionsΔρmin = 0.27 e Å3
57 parameters
Special details top

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.67794 (13)0.21313 (14)0.19921 (8)0.0230 (4)
C40.78247 (19)0.10828 (18)0.18768 (11)0.0320 (5)
H4A0.83630.08890.20350.038*
C50.75801 (15)0.18462 (15)0.22066 (10)0.0235 (4)
C10.62321 (18)0.16518 (17)0.14468 (10)0.0282 (4)
H1A0.56760.18310.13000.034*
C30.7263 (2)0.06123 (18)0.13113 (11)0.0351 (5)
H3A0.74260.01090.10830.042*
C20.64568 (19)0.09035 (18)0.10931 (11)0.0330 (5)
H2A0.60700.06020.07140.040*
Fe0.66670.33330.25000.0189 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0212 (8)0.0185 (7)0.0269 (8)0.0080 (6)0.0015 (6)0.0005 (6)
C40.0328 (11)0.0257 (10)0.0409 (12)0.0172 (9)0.0057 (9)0.0022 (9)
C50.0208 (8)0.0183 (8)0.0317 (10)0.0101 (7)0.0039 (7)0.0028 (7)
C10.0277 (10)0.0244 (9)0.0301 (11)0.0112 (8)0.0026 (8)0.0038 (8)
C30.0434 (12)0.0234 (10)0.0391 (12)0.0170 (10)0.0108 (10)0.0029 (8)
C20.0338 (11)0.0256 (10)0.0332 (11)0.0101 (9)0.0010 (9)0.0061 (8)
Fe0.0170 (2)0.0170 (2)0.0229 (3)0.00848 (12)0.0000.000
Geometric parameters (Å, º) top
N1—C11.345 (3)C3—C21.378 (3)
N1—C51.364 (2)C3—H3A0.9300
N1—Fe1.9841 (16)C2—H2A0.9300
C4—C31.386 (3)Fe—N1i1.9841 (16)
C4—C51.391 (3)Fe—N1ii1.9841 (16)
C4—H4A0.9300Fe—N1iii1.9841 (16)
C5—C5i1.460 (4)Fe—N1iv1.9841 (16)
C1—C21.386 (3)Fe—N1v1.9841 (16)
C1—H1A0.9300
C1—N1—C5117.79 (17)C1—C2—H2A120.5
C1—N1—Fe127.46 (13)N1i—Fe—N181.67 (9)
C5—N1—Fe114.53 (13)N1i—Fe—N1ii93.16 (6)
C3—C4—C5119.7 (2)N1—Fe—N1ii92.47 (9)
C3—C4—H4A120.1N1i—Fe—N1iii92.47 (9)
C5—C4—H4A120.1N1—Fe—N1iii93.16 (6)
N1—C5—C4121.47 (19)N1ii—Fe—N1iii172.56 (9)
N1—C5—C5i114.54 (11)N1i—Fe—N1iv93.16 (6)
C4—C5—C5i123.98 (13)N1—Fe—N1iv172.56 (9)
N1—C1—C2123.20 (19)N1ii—Fe—N1iv93.16 (6)
N1—C1—H1A118.4N1iii—Fe—N1iv81.67 (9)
C2—C1—H1A118.4N1i—Fe—N1v172.56 (9)
C2—C3—C4118.81 (19)N1—Fe—N1v93.16 (6)
C2—C3—H3A120.6N1ii—Fe—N1v81.67 (9)
C4—C3—H3A120.6N1iii—Fe—N1v93.16 (6)
C3—C2—C1119.0 (2)N1iv—Fe—N1v92.47 (9)
C3—C2—H2A120.5
Symmetry codes: (i) y+1, x+1, z+1/2; (ii) x+y+1, y, z+1/2; (iii) y+1, xy, z; (iv) x, xy, z+1/2; (v) x+y+1, x+1, z.

Experimental details

(I)(II)
Crystal data
Chemical formulaC30H24N6RuCl2·6(H2O)C30H24FeN6·2(NCS)
Mr748.62642.28
Crystal system, space groupHexagonal, P6/mccHexagonal, P6/mcc
Temperature (K)150150
a, c (Å)13.1383 (12), 20.995 (3)13.1837 (9), 21.2735 (14)
V3)3138.6 (6)3202.2 (4)
Z44
Radiation typeMo KαMo Kα
µ (mm1)0.720.20
Crystal size (mm)0.21 × 0.16 × 0.120.18 × 0.12 × 0.10
Data collection
DiffractometerRigaku Saturn724+ (2x2 bin mode)
diffractometer
Rigaku Saturn724+ (2x2 bin mode)
diffractometer
Absorption correctionEmpirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
Empirical (using intensity measurements)
CrystalClear (Rigaku Inc., 2008)
Tmin, Tmax0.676, 1.0000.857, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
11174, 1220, 994 26491, 1259, 1165
Rint0.0860.043
(sin θ/λ)max1)0.6500.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.061, 0.153, 1.09 0.049, 0.115, 1.13
No. of reflections12201259
No. of parameters5757
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.98, 0.560.32, 0.27

Computer programs: CrystalClear (Rigaku Inc., 2008), SHELXS97 (Sheldrick, 2008), SIR92 (Altomare et al., J. Appl. Cryst. (1994). 27, 435), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), WinGX publication routines (Farrugia, 1999).

 

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