F or O, Which One Is the Better Hydrogen Bond (Is It?) Acceptor in C

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F or O, Which One is the Better Hydrogen Bond (is It?) Acceptor in the C-H...X-C (X- = F-, O=) Interactions? Binoy K. K. Saha, Arijit Saha, Durgam Sharada, and Sumair A. Rather Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b01164 • Publication Date (Web): 20 Nov 2017 Downloaded from http://pubs.acs.org on November 29, 2017

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Crystal Growth & Design

F or O, Which One is the Better Hydrogen Bond (is It?) Acceptor in the C− −H⋅⋅⋅⋅X− −C (X− − = F− −, O=) Interactions? Binoy K. Saha*, Arijit Saha,‡ Durgam Sharada‡ and Sumair A. Rather‡ Department of Chemistry, Pondicherry University, Puducherry 605 014, India, KEYWORDS Statistical analysis, hydrogen bond, weak interactions, geometrical correction

ABSTRACT Three sets of statistical analyses have been performed to evaluate which one between C−F and C=O is the better C−H hydrogen bond acceptor and to understand the nature and preferred geometry of the C−H⋅⋅⋅F−C interactions. The first analysis uses Hirshfeld surface of the molecules which shows that C=O is a better hydrogen bond acceptor than C−F, though C−H⋅⋅⋅F−C interactions also play an important role in crystal packing. The second analysis compares the population densities of C−H⋅⋅⋅F−C interactions at different H⋅⋅⋅F distances and at different C−H⋅⋅⋅F or C−F⋅⋅⋅H angles. This analysis shows the directional nature of this interaction. The third analysis shows which combinations of the C−H⋅⋅⋅F and C−F⋅⋅⋅H angles are preferred by the C−H⋅⋅⋅F−C interactions.

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Introduction Supramolecular interactions are in the heart of crystal engineering and solid-state chemistry.1 Conventional hydrogen bonds are at one end of the wide range of spectrum of these interactions and van der Waals interactions are at the other end. Conventional hydrogen bonds, such as O−H⋅⋅⋅O, O−H⋅⋅⋅N, N−H⋅⋅⋅O are known as directional and strong interactions, whereas the van der Waals interactions are known as non-directional and weak interactions.2-5 There is a plethora of other interactions that bridge between these two extreme ends. Most common type of interactions in this category are C−H⋅⋅⋅O/N, N/O−H⋅⋅⋅halogen, C−H⋅⋅⋅π, halogen⋅⋅⋅O/N, halogen…halogen etc.6,7 C−H⋅⋅⋅O/N interactions are now widely accepted as weak hydrogen bonds8-12 but the nature of C−H⋅⋅⋅halogen−C interactions is still a matter of debate. Among the C−H⋅⋅⋅halogen−C interactions, the C−H⋅⋅⋅F−C interaction is the most debated one because of the widespread presence of F in different materials and biological systems.13 A group of thoughts considers this as a van der Waals interaction,9,14 whereas other group thinks it should fall in the category of weak hydrogen bonding.15-17 X-ray crystal structures, theoretical calculations, charge density calculations have been the tools to assess the nature of these interactions. But the most popular tool, in this regard, perhaps is the statistical analysis on the reported data base available in CCDC. Here we have performed statistical analyses on the C−H⋅⋅⋅X−C (X = F, O) interactions data, retrieved from CCDC,18 to see which one, between O and F, is the better hydrogen bond acceptor and to understand the nature and geometry of the C−H⋅⋅⋅F−C interactions. Because C−H⋅⋅⋅O=C has been widely accepted as hydrogen bond, if F is found to be a better acceptor than O, then C−H⋅⋅⋅F−C interaction should also be considered as hydrogen bond and hence an important determining factor in crystal packing. But if it is weaker than O, then the question arises is whether this interaction still a significant one or merely a result of random distribution? What would be the preferred geometry of the C−H⋅⋅⋅F−C interactions if it is not an isotropic van der Waals interaction? Based on statistical analysis and energy calculation, Gavezotti and Lo Presti have concluded that this interaction is not more than a van der Waals interaction.9 Their energy calculations show that the Coulombic contribution in the interactions is very small. They used very strict distance cut-off criteria in their study. Similarly, based on statistical analysis with the H⋅⋅⋅F distances
1 then the interaction is more than what would have been expected from

just a random distribution and hence it is stabilizing. We also have calculated the % surface area on X covered by the interacting atom Y as actually observed and based on random distribution. The observed % area on X covered by Y is given by OBY-X% =

( ) ! (")

× 100… (5)

and based on random orientation of the molecules, the % surface area of X covered by Y is given by RAY-X% =

( ) ! (")

× 100… (6)

Therefore, the excess surface area on X occupied by Y is given by EXY-X% = OBY-X% − RAY-X% … (7) Distance-cone and double area corrections CCDC database was searched (version 5.38, November 2016) for the structures containing H⋅⋅⋅F distance range 2.00 − 4.00 Å, C−H⋅⋅⋅F and C−F⋅⋅⋅H angles in the C−H⋅⋅⋅F−C interactions 90−180°, 3D coordinates available, neutron normalized, R-factor ≤ 10 %, Only organic. This data set comprised a total of 24,439 number of structures with 4,33,499 number of H⋅⋅⋅F contacts. Distance-cone correction The equation of volume of space confined within the angle range θ1→θ2 and distance range r1→r2 (Scheme 1) is given by Vθ1θ2,r1r2 =

# $

π(%#$ − %$ )('()θ − '()θ# )

The population density or distance-cone corrected population is given by Ndis-cone =

*θ+θ,,.+., /θ+θ,,.+.,

….(8)

Nθ1θ2,r1r2 is the number of H or F atoms present within the volume of space, Vθ1θ2,r1r2 around the C−F or C−H groups respectively, participating in C−H⋅⋅⋅F−C interaction. % of Ndis-cone values have been tabulated in Table 1 and Table 2.


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Double area correction The double area corrected population27 has been calculated as OP/CP, where OP and CP are the observed population and calculated population based on random distribution respectively for the angle ranges θH→(θH − 10) around H and θF→(θF − 10) around F in the C−H⋅⋅⋅F−C interactions. OP has been obtained from the CSD search and CP has been calculated as CP =

θ0 →(θ +1) 0 0(+21→31)

×

θ4 →(θ +1) 4 4(+21→31)

×N

= [cos(θH − 10) − cosθH][cos(θF − 10) − cosθF] × N ….(9) Here, N is the total number of H⋅⋅⋅F interactions within the distance range 2.0 − 4.0 Å, θ0→(θ0 5) and θ4 →(θ4 5) are the surface areas on H and F for the angle ranges θ6 →(θ6 − 10) and θ9 →(θ9 − 10) respectively, 6(:→;) and 9(:→;) are the surface areas on H and F for the angle ranges 90→180° respectively, θH and θF values are 180°, 170°, …, 100°. Then the OP/CP % population ratio vs. θF and θH has been plotted in Figure 2.

Results and Discussion We have analyzed the ratio of the observed Y⋅⋅⋅X contact surface area and the calculated Y⋅⋅⋅X contact surface area if the molecules were randomly oriented in the crystal structures (OBY-X / RAY-X) from equation (3) and (4). We also have analyzed the observed % surface area of X occupied by Y (OBY-X%) from equation (5) and calculated % surface area of X occupied by Y (RAY-X%) if the molecules were randomly oriented in the crystal structures from equation (6). Next we found out the excess % surface area of X occupied by Y with respect to the random orientation of the molecules (EXY-X%) from equation (7). Then we compared these OBY-X / RAYX,

OBY-X% and EXY-X% values for different types of interactions. From Figure 1 it is apparent that

the OBY-X / RAY-X (Figure 1a), OBY-X% (Figure 1b) and EXY-X% (Figure 1c) values are higher for the C−H⋅⋅⋅O=C interaction compared to those for the C−H⋅⋅⋅F−C interactions. From the calculations on 132 individual structures, it has been noticed that there are 87 cases where the % surface area of O atoms occupied by H atoms is higher than that of F occupied by H, whereas in only 38 cases the trend is found to be reversed, and in 7 cases both the values are same. It may be noted here that maximum hydrogen bonding by an acceptor can be attained when the surface of that particular acceptor is totally saturated by H or the surface of the H is totally saturated by that


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particular acceptor. Therefore, it is clear that C−H⋅⋅⋅O=C interaction is more stabilizing than C−H⋅⋅⋅F−C in contrast to what was found in Taylors study.16 Nevertheless, all these parameters indicate that the C−H⋅⋅⋅F−C interaction is quite significant, not just a result of random distribution which is in agreement with Taylors finding. It may be noted here that some of the reported theoretical calculations also support the hydrogen bonding nature in the C−H⋅⋅⋅F−C interactions.28-31 Even though the electrostatic contribution in H⋅⋅⋅F is expected to be higher than that in H⋅⋅⋅O interaction, due to hard nature of F atom, the orbital overlap between H and F is poorer than that between H and O. The overall effect is that the C−H⋅⋅⋅O=C is found to be a stronger interaction than C−H⋅⋅⋅F−C. We also checked if the conjugation with the C=O group makes O a better acceptor than F. There are 22 structures among these 132 data where none of the C=O groups in the molecules is conjugated to any double bond or aromatic ring. A similar analysis on this data set suggests that O is still a better acceptor than F, though acceptor ability of O is reduced. In this set of 22 structures, the OBY-X / RAY-X value does not change significantly for F (OBY-X / RAY-X = 1.29 for 132 data and 1.28 for 22 data), but it certainly decreases for O (OBY-X / RAY-X = 1.40 for 132 data and 1.33 for 22 data). The excess population of H on F surface also remains almost unchanged (13.8 % for 132 data and 14.1 % for 22 data), but it decreases in the case of O (22.8 % for 132 data and 19.4 % for 22 data). The observed population of the H⋅⋅⋅C interactions is close to the random population distribution. On the other hand, among the homo diatomic interactions, it is observed that the occurrence of H⋅⋅⋅H and F⋅⋅⋅F interactions are slightly lesser than what would have been expected from a random contact distribution. Among the four elements present in these molecules, H is the most electro positive and F is the most electro negative elements and hence the electrostatic contribution of the H⋅⋅⋅H and F⋅⋅⋅F interactions might be somewhat repulsive in nature. This statistical analysis does not tell whether a contact is overall attractive or repulsive, it only tells about the relative population and hence the relative stability. As we are studying the solid state crystal structure, the net interactions are stabilizing. Therefore, the H⋅⋅⋅H and F⋅⋅⋅F interactions could be mildly repulsive or only very weakly stabilizing. It is worth to mention here that in the crystal structure of a molecule containing X, Y and Z types of atoms, if the X⋅⋅⋅Y interaction is highly stabilizing, then X⋅⋅⋅Y contact area would be much higher than what would have been expected from a random orientation of the molecules, but at the same time X⋅⋅⋅X, Y⋅⋅⋅Y, X⋅⋅⋅Z and Y⋅⋅⋅Z contact areas


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might be smaller than what would have been expected from a random distribution even if these four interactions are weakly stabilizing in nature. Among the homo atomic interactions, C⋅⋅⋅C is found to be the most abundant here. As H, F and O are mainly involved in H⋅⋅⋅F and H⋅⋅⋅O interactions, C is left alone to interact with itself. It may be noted that the surface areas of sp3-C atoms are generally not exposed for intermolecular interactions. Therefore, the C surface refers to only π bonded carbons. It is evident from the plots that the F⋅⋅⋅O and O⋅⋅⋅O contacts are least stabilizing or most repulsive among all the possible interacting atom pairs presented here. From this analysis it is clear that F⋅⋅⋅F is relatively better than these two interactions, indicating special characteristic of the halogen⋅⋅⋅halogen interactions.24,32,33 The ratio of surface areas (SX(i) + SX(e)) of C, H, F and O in this method for the 132 structures is found to be 2.33 : 8.65 : 2.66 : 1. It may be noted that unlike CPK model, almost the entire Hirshfeld surface area of the atoms in a molecule is involved in intermolecular interactions.34 Next we were interested to investigate the preferred geometry of the C−H⋅⋅⋅F−C interactions. In their interesting Isotropic Density Correction, Seddon and Berg calculated the population density at different C−H⋅⋅⋅F angles and H⋅⋅⋅F distances.23 Then compared this population with the average population density and argued that if the density at a particular angle and distance is higher than the average density then that geometry is preferred. But the average density depends upon the distance range of H⋅⋅⋅F considered which is arbitrary. Therefore, in our work we have not compared the observed population with the average population density. Rather we have just calculated the population density at different C−H⋅⋅⋅F angles (θH) and H⋅⋅⋅F distances (dHF) and these population densities were then compared (Table 1). We also have performed same study for the C−F⋅⋅⋅H angles (θF) to understand the complete preferred geometry of the C−H⋅⋅⋅F−C interactions (Table 2). For comparison we have executed similar analyses on C−H⋅⋅⋅O=C interactions too and showed in Table S19 and Table S21 (supporting information). It can be seen from Table 1 and Table 2 that the population density is maximum at higher angle (170 − 180°) and as the angle (C−H⋅⋅⋅F or C−F⋅⋅⋅H) decreases, the H⋅⋅⋅F distance increases. The directionality is found to be more prominent around the C−H⋅⋅⋅F angle rather than around the C−F⋅⋅⋅H angle. H atom is smaller and possesses a relatively high positive electrostatic potential at around 180°. On the other side, F is hard, relatively larger and more or less isotropic. But as the angle (C−H⋅⋅⋅F or C−F⋅⋅⋅H) decreases, the steric hindrance increases. Due to all these factors


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highest density is found at around 180° in both the cases and C−H⋅⋅⋅F shows a higher directionality than C−F⋅⋅⋅H. It may be noted that the highest density observed at θH = 170 − 180° is at much smaller H⋅⋅⋅F distance than the distance at θF = 170 − 180°. This indicates that at very short H⋅⋅⋅F distance the C−H⋅⋅⋅F angles prefer to be linear but a large number of C−F⋅⋅⋅H angles adopt bent geometry. It is worth to mention here that according to Table S21 the C−H⋅⋅⋅O interaction in C−H⋅⋅⋅O=C is even more directional than the corresponding C−H⋅⋅⋅F counterpart. We were also interested to see which combinations of the C−H⋅⋅⋅F and C−F⋅⋅⋅H angles are preferentially adopted by the C−H⋅⋅⋅F−C interactions. We have used the data base, searched for the distance−angle correction of the C−H⋅⋅⋅F−C interactions and performed double area correction27 on H and F atoms (Figure 2). At lower θF (90 − 120°) the population increases as the θH value increases from 90 to 180°, but at higher θF (170 − 180°) the population at first increases till θH = 130°, then decreases till 140 − 150° and then again increases till 170 − 180°. On the other hand, at lower angle of θH = 90 − 110° the population remains almost constant for the range of θF = 100 − 180°. But at higher angle of θH = 170 − 180°, the population at first increases from θF = 90 to 130° then decreases and then again increases near θF = 170 − 180°. It may be noted that at θH = 170 − 180°, the pattern of population distribution at different θF is similar to the distribution found in C−F⋅⋅⋅F−C interaction reported in one of our previous works.27 As both the atoms, F and H have highest density at 170 − 180° (Table 1 and Table 2), the highest population is found at θH as well as θF = 170 − 180°.

Conclusions As Taylor has commented that the atoms have to stay somewhere in the crystal, therefore, whether C−H⋅⋅⋅F−C interactions are energetically highly favorable or not, this study shows that C−H⋅⋅⋅F−C interaction is definitely more favorable than C−H⋅⋅⋅π as well as C−F⋅⋅⋅F−C interactions and C−H⋅⋅⋅F−C interactions occur more frequently than what would have been expected from a random distribution of the interacting atoms. Nevertheless, as a hydrogen bond acceptor C−F group is not as good as C=O. Due to hard nature of F, unlike short H⋅⋅⋅O bond distance, the preferred H⋅⋅⋅F contact distance is around the sum of van der Waals radii of H and F. Interestingly the preferred angles around the H as well as F atoms in the C−H⋅⋅⋅F−C interactions are linear. Our study supports the observation by Glusker et al. where they


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commented that though the role of C−H⋅⋅⋅F−C interactions cannot be ignored in crystal packing, the C−F group is not competent to C−O or C=O group as hydrogen bond acceptor35 and Desiraju’s observation on hydrogen bridge interactions without border.6

Scheme 1. Volume of space (ring) confined within the distance range r1 to r2 from X atom and angle range θ1 to θ2 around the C−X bond is shown here.

(a)


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(b)

(c) Figure 1. (a) Observed / random population ratios (OBY-X / RAY-X) for different interactions. (b) % of surface areas of the different types of atoms occupied by C (red), H (green), F (blue) and O (sky blue) are shown. (c) Excess surface area on different types of atoms in comparison to what would have been expected from a random distribution of the molecules occupied by C (red), H (green), F (blue) and O (sky blue) are shown.


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Figure 2. 3D plot of % population distribution (H⋅⋅⋅F = 2.00 − 4.00 Å) at different combinations of θH and θF obtained after double area correction. Table 1. % Populations of C−H…F−C after distance-cone correction at different combinations of θH and H⋅⋅⋅F distance (dHF). Populations in the ranges 3.68−4.00 and 2.00−2.16 Å are very small (< 0.200 %) and are not shown in the table. Color code % population Color code % population 3.640-3.68 3.60-3.64 3.56-3.60 3.52-3.56 3.48-3.52 3.44-3.48 3.40-3.44 3.36-3.40 3.32-3.36 3.28-3.32 3.24-3.28 3.20-3.24 3.16-3.20 3.12-3.16

0.000- 0.100- 0.200- 0.300- 0.400- 0.500- 0.6000.099 0.199 0.299 0.399 0.499 0.599 0.699 0.700- 0.8000.799 0.899

0.148 0.163 0.172 0.178 0.188 0.198 0.198 0.222 0.227 0.251 0.250 0.270 0.277 0.281

0.150 0.159 0.173 0.174 0.189 0.201 0.206 0.225 0.232 0.249 0.269 0.279 0.302 0.327

0.119 0.123 0.134 0.139 0.156 0.161 0.178 0.183 0.204 0.230 0.249 0.265 0.289 0.323

0.116 0.115 0.121 0.117 0.127 0.139 0.141 0.152 0.167 0.178 0.196 0.206 0.233 0.261

0.118 0.119 0.127 0.134 0.131 0.140 0.150 0.167 0.171 0.177 0.177 0.220 0.211 0.244

0.097 0.103 0.108 0.113 0.117 0.128 0.140 0.148 0.163 0.184 0.187 0.208 0.214 0.239

0.100 0.103 0.113 0.118 0.118 0.125 0.133 0.141 0.149 0.165 0.164 0.175 0.210 0.205

0.095 0.106 0.106 0.104 0.115 0.125 0.124 0.136 0.138 0.145 0.182 0.178 0.217 0.201

0.096 0.092 0.099 0.095 0.105 0.130 0.122 0.154 0.148 0.134 0.145 0.187 0.178 0.195


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3.08-3.12 3.04-3.08 3.00-3.04 2.96-3.00 2.92-2.96 2.88-2.92 2.84-2.88 2.80-2.84 2.76-2.80 2.72-2.76 2.68-2.72 2.64-2.68 2.60-2.64 2.56-2.60 2.52-2.56 2.48-2.52 2.44-2.48 2.40-2.44 2.36-2.40 2.32-2.36 2.28-2.32 2.24-2.28 2.20-2.24 2.16-2.20 dHF θH

0.294 0.287 0.281 0.256 0.241 0.216 0.185 0.151 0.113 0.078 0.056 0.033 0.019 0.011 0.008 0.004 0.001 0.001 0.000 0.001 0.001 0.000 0.000 0.000 90100

0.347 0.351 0.378 0.377 0.401 0.387 0.377 0.365 0.316 0.278 0.225 0.178 0.126 0.085 0.050 0.028 0.017 0.010 0.004 0.004 0.001 0.001 0.001 0.000 100110

0.352 0.368 0.418 0.447 0.473 0.519 0.548 0.548 0.559 0.543 0.498 0.458 0.376 0.298 0.242 0.156 0.099 0.059 0.026 0.011 0.007 0.003 0.003 0.001 110120

0.290 0.293 0.346 0.377 0.419 0.457 0.508 0.539 0.558 0.612 0.624 0.623 0.587 0.560 0.476 0.399 0.292 0.192 0.123 0.063 0.036 0.016 0.008 0.004 120130

0.274 0.286 0.311 0.337 0.367 0.392 0.432 0.482 0.509 0.539 0.569 0.596 0.630 0.599 0.556 0.503 0.407 0.314 0.212 0.153 0.077 0.049 0.025 0.009 130140

0.249 0.282 0.300 0.327 0.361 0.400 0.429 0.470 0.521 0.540 0.584 0.601 0.604 0.647 0.591 0.584 0.518 0.450 0.306 0.230 0.132 0.089 0.043 0.015 140150

0.225 0.225 0.293 0.324 0.335 0.357 0.391 0.458 0.499 0.559 0.575 0.626 0.677 0.682 0.669 0.656 0.615 0.508 0.421 0.315 0.195 0.137 0.077 0.040 150160

0.242 0.248 0.297 0.301 0.330 0.370 0.378 0.434 0.494 0.550 0.568 0.629 0.663 0.694 0.683 0.680 0.670 0.637 0.489 0.385 0.267 0.187 0.085 0.050 160170

0.206 0.243 0.290 0.334 0.334 0.387 0.384 0.476 0.512 0.565 0.611 0.686 0.694 0.758 0.725 0.828 0.729 0.630 0.609 0.431 0.273 0.205 0.109 0.068 170180

Table 2. % Populations of C−H…F−C after distane-angle correction at different combinations of θF and H⋅⋅⋅F distance (dHF). Populations in the ranges 3.88−4.00 and 2.00−2.20 Å are very small (< 0.200 %) and are not shown in the table. Color code % population 3.84-3.88 3.80-3.84 3.76-3.80 3.72-3.76 3.68-3.72 3.64-3.68 3.60-3.64 3.56-3.60 3.52-3.56 3.48-3.52 3.44-3.48 3.40-3.44 3.36-3.40 3.32-3.36 3.28-3.32 3.24-3.28

000- 0.100- 0.200- 0.300- 0.400- 0.500- 0.6000.099 0.199 0.299 0.399 0.499 0.599 0.699

0.142 0.145 0.143 0.144 0.152 0.152 0.164 0.174 0.177 0.183 0.188 0.197 0.212 0.219 0.238 0.252

0.131 0.131 0.141 0.139 0.156 0.160 0.163 0.165 0.173 0.182 0.201 0.204 0.225 0.231 0.260 0.265

0.105 0.107 0.116 0.111 0.124 0.125 0.132 0.148 0.144 0.162 0.174 0.185 0.195 0.218 0.228 0.251

0.092 0.102 0.106 0.104 0.113 0.118 0.121 0.129 0.139 0.135 0.157 0.158 0.179 0.178 0.204 0.217

0.095 0.097 0.101 0.107 0.111 0.116 0.111 0.128 0.130 0.138 0.150 0.156 0.174 0.187 0.194 0.201

0.091 0.098 0.107 0.103 0.107 0.106 0.116 0.126 0.124 0.137 0.141 0.149 0.156 0.169 0.191 0.196

0.098 0.102 0.098 0.106 0.106 0.108 0.120 0.126 0.124 0.136 0.132 0.154 0.162 0.173 0.173 0.192

0.108 0.087 0.116 0.103 0.112 0.110 0.122 0.129 0.131 0.152 0.150 0.145 0.156 0.170 0.189 0.190

0.097 0.096 0.091 0.106 0.095 0.110 0.121 0.110 0.133 0.134 0.133 0.137 0.163 0.189 0.193 0.184


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3.20-3.24 3.16-3.20 3.12-3.16 3.08-3.12 3.04-3.08 3.00-3.04 2.96-3.00 2.92-2.96 2.88-2.92 2.84-2.88 2.80-2.84 2.76-2.80 2.72-2.76 2.68-2.72 2.64-2.68 2.60-2.64 2.56-2.60 2.52-2.56 2.48-2.52 2.44-2.48 2.40-2.44 2.36-2.40 2.32-2.36 2.28-2.32 2.24-2.28 2.20-2.24 dHF θF

0.257 0.262 0.280 0.292 0.285 0.301 0.299 0.296 0.284 0.276 0.274 0.257 0.238 0.215 0.178 0.159 0.134 0.101 0.080 0.058 0.037 0.018 0.010 0.008 0.003 0.001 90100

0.282 0.306 0.332 0.342 0.346 0.375 0.376 0.384 0.402 0.401 0.410 0.411 0.393 0.366 0.353 0.303 0.266 0.220 0.184 0.131 0.086 0.055 0.040 0.021 0.012 0.004 100110

0.277 0.292 0.320 0.354 0.360 0.397 0.432 0.453 0.480 0.499 0.528 0.528 0.543 0.509 0.499 0.462 0.414 0.358 0.306 0.250 0.182 0.123 0.070 0.033 0.020 0.014 110120

0.231 0.255 0.278 0.295 0.320 0.373 0.385 0.416 0.435 0.472 0.512 0.514 0.511 0.512 0.530 0.516 0.502 0.452 0.405 0.330 0.263 0.182 0.131 0.074 0.045 0.020 120130

0.216 0.240 0.256 0.291 0.298 0.349 0.363 0.399 0.427 0.443 0.478 0.477 0.499 0.515 0.541 0.516 0.504 0.457 0.410 0.355 0.298 0.203 0.157 0.095 0.061 0.036 130140

0.221 0.236 0.248 0.289 0.300 0.345 0.356 0.392 0.439 0.445 0.447 0.473 0.508 0.519 0.506 0.513 0.509 0.491 0.446 0.385 0.323 0.248 0.193 0.121 0.076 0.040 140150

Page 14 of 18

0.219 0.241 0.262 0.292 0.300 0.312 0.343 0.393 0.385 0.430 0.444 0.464 0.512 0.540 0.522 0.527 0.522 0.506 0.480 0.427 0.362 0.296 0.208 0.122 0.104 0.047 150160

0.233 0.230 0.247 0.275 0.306 0.316 0.347 0.360 0.410 0.470 0.459 0.510 0.522 0.515 0.561 0.576 0.583 0.517 0.512 0.456 0.402 0.308 0.213 0.146 0.105 0.050 160170

0.224 0.256 0.252 0.281 0.298 0.316 0.351 0.392 0.415 0.464 0.463 0.499 0.541 0.600 0.530 0.586 0.582 0.547 0.527 0.491 0.381 0.305 0.216 0.170 0.113 0.069 170180

Supporting Information. The refcode list for the structures containing C, H, F and O elements and some relevant tables are given. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author Dr. Binoy K. Saha, Department of Chemistry, Pondicherry University, Puducherry 605 014, India. E-mail: [email protected] Author Contributions ‡These authors contributed equally.


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Funding Sources B.K.S. thanks Council of Scientific and Industrial Research, India (01(2908)/17/EMR-II) for financial support, AS and SAR thank Pondicherry University and DS thanks RGNF for fellowship. REFERENCES 1. Desiraju, G. R. Angew. Chem. Int. Ed. 1995, 34, 2311−2327. 2. Kroon, J.; Kanters, J. A. Nature 1974, 248, 667−669. 3. Nangia, A. CrystEngComm 2002, 4, 93−101. 4. Steiner, T. Angew. Chem. Int. Ed. 2002, 41, 48–76. 5. Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in Structural Chemistry and Biology, Oxford University Press: Oxford, 1999. 6. Desiraju, G. R. Acc. Chem. Res., 2002, 35, 565−573. 7. Cavallo, G.; Metrangolo, P.; Milani, R.; Pilati, T.; Priimagi, A.; Resnati, G.; Terraneo, G. Chem. Rev. 2016, 116, 2478−2601. 8. Steiner, T.; Desiraju, G. R. Chem. Commun., 1998, 891−892. 9. Gavezzotti, A.; Lo Presti, L. Cryst. Growth Des. 2016, 16, 2952−2962. 10. Desiraju, G. R. Acc. Chem. Res. 1996, 29, 441−449. 11. Gu, Y.; Kar, T.; Scheiner, S. J. Am. Chem. Soc. 1999, 121, 9411−9422. 12. Bernstein, J. Cryst. Growth Des. 2013, 13, 961−964. 13. Meyer, E. A.; Castellano, R. A.; Diederich, F. Angew. Chem. Int. Ed. 2003, 42, 1210–1250. 14. Dunitz, J. D.; Taylor, R. Chem. Eur. J. 1997, 3, 89−98. 15. Chopra, D.; Guru Row, T. N. CrystEngComm 2011, 13, 2175–2186.


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16. Taylor, R. Cryst. Growth Des. 2016, 16, 4165−4168. 17. Chopra, D. Cryst. Growth Des. 2012, 12, 541−546. 18. The Cambridge Structural Database version 5.38. ConQuest 1.19; Cambridge Crystallographic Data Centre: Cambridge, U.K., November 2016. 19. Chopra, D.; Cameron, T. S.; Ferrara, J. D.; Guru Row, T. N. J. Phys. Chem. A 2006, 110, 10465−10477. 20. Choudhury A. R.; Guru Row, T. N. Cryst. Growth Des. 2004, 4, 47−52. 21. Thalladi, V. A.; Weiss, H. C.; Bläser, D.; Boese, R.; Nangia, A.; Desiraju, G. R. J. Am. Chem. Soc. 1998, 120, 8702–8710. 22. Brammer, L.; Bruton, E. A.; Sherwood, P. Cryst. Growth Des. 2001, 1, 277–290. 23. Berg, J. A. V.; Seddon, K. R. Cryst. Growth Des. 2003, 3, 643–661. 24. Infantes, L.; Motherwell, S. Struct. Chem. 2004, 15, 173−184. 25. Spackman, M. A.; Jayatilaka, D. CrystEngComm, 2009, 11,19−32. 26. Turner, M. J.; McKinnon, J. J.; Wolff, S. K.; Grimwood, D. J.; Spackman, P. R.; Jayatilaka, D; Spackman, M. A. CrystalExplorer17, 2017, University of Western Australia. 27. Saha, B. K.; Saha, A.; Rather, S. A. Cryst. Growth Des. 2017, 17, 2314−2318. 28. Hyla-Kryspin, I.; Haufe, G.; Grimme, S. Chem. Eur. J. 2004, 10, 3411−3422. 29. O’Oria, E. D.; Novoa, J. J. CrystEngComm 2008, 10, 423−436. 30. Hyla-Kryspin, I.; Haufe, G.; Grimme, S. Chem. Phys. 2008, 346, 224−236. 31. Rybalova, T. V.; Bagryanskaya, I. Y. J. Struct. Chem. 2009, 50, 741−753. 32. Desiraju, G. R.; Parthasarathy, R. J. Am. Chem. Soc. 1989, 111, 8725−8726. 33. Awwadi, F. F.; Willett, R. D.; Peterson, K. A.; Twamley, B. Chem. Eur. J. 2006, 12, 8952−8960.


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34. McKinnon, J. J.; Mitchell, A. S.; Spackman, M. A. Chem. Eur. J. 1998, 4, 2136−2141. 35. Shimoni, L.; Glusker, J. P. Struct. Chem. 1994, 5, 383−397.


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Table of Contents

F or O, Which One is the Better Hydrogen Bond (is It?) Acceptor in the C− −H⋅⋅⋅⋅X− −C (X− − = F− −, O=) Interactions? Binoy K. Saha*, Arijit Saha,‡ Durgam Sharada‡ and Sumair A. Rather‡

C−H⋅⋅⋅F−C interactions are directional and attractive but weaker than C−H⋅⋅⋅O=C interactions.


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F or O, Which One Is the Better Hydrogen Bond (Is It?) Acceptor in C

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