Asymmetric rotations and dimerization driven by normal to modulated phase transition in 4-biphenylcarboxy coupled l-phenylalaninate

Crystals of a coupled molecule of 4-biphenylcarboxy-(l)-phenylalaninate undergo normal to commensurately modulated phase transition at T c ∼ 124 K that is characterized by torsional modulation typical of modulated structures and superstructures of polyphenyls yet unusual owing to asymmetric and unequal rotations governed by intramolecular and intermolecular constraints. The transition is presumably governed by significant suppression of atomic displacement parameters correlated to the evolution of amplitude of atomic modulation functions.

T = 100 K suggests that the phase transition drives the biphenyl moieties towards non coplanar conformations with significant variation of internal torsion (ϕ max biphenyl ≤ 20 degrees).These intramolecular rotations lead to dimerization of the molecular stacks that are described predominantly by intermolecular tilts and small variations in intermolecular distances.Atypical of modulated structures and superstructures of biphenyl and other polyphenyls, the rotations of individual molecules are asymmetric (∆ϕ biphenyl ≈ 5 degrees) while ϕ biphenyl of one independent molecule is two to four times larger than the other.Crystal-chemical analysis and phase relations in  (Bastiansen, 1949;Suzuki, 1959;Trotter, 1961;Hargreaves & Rizvi, 1962).The planar conformation due to constraints from intermolecular interactions is energetically unfavourable and steric hindrance between the ortho hydrogen atoms is compensated for by out of plane dynamic disorder and in plane displacements of those hydrogens away from each other (Hargreaves & Rizvi, 1962;Casalone et al., 1968;Charbonneau & Delugeard, 1976;Charbonneau & Delugeard, 1977;Busing, 1983;Lenstra et al., 1994) A recent study has also suggested the role of intramolecular exchange energy between single bonded carbon atoms in stabilizing IUCr macros version 2.1.15:2021/03/05 the planar conformation (Popelier et al., 2019).Absorption and fluorescence studies showed additional bands in their spectra at low temperatures (T ) (Hochstrasser et al., 1973;Wakayama, 1981).T -dependent Raman spectroscopy and Brillouin scattering experiments have suggested two phase transitions at T c1 = 42 K and T c2 = 17 K respectively (Friedman et al., 1974;Bree & Edelson, 1977;Bree & Edelson, 1978;Ecolivet & Sanquer, 1983).The phase transition at T c1 is continuous and governed by a soft mode associated with the torsion about the central C-C single bond followed by discontinuous changes at T c2 .Inelastic neutron scattering experiments on its deuterated form confirmed the phase transitions with appearance of additional satellite reflections (Cailleau et al., 1978).The modulation wave vector (q) was determined to be q I = δ a a * + 1 2 (1 − δ b )b * and q II = 1 2 (1 − δ b )b * at the intermediate and low temperature phases respectively and were found to vary with temperature, suggesting an incommensurate nature of the modulation (Cailleau et al., 1978).The modulated structure of the low temperature phase II was described within an acentric superspace group symmetry P a(0σ 2 0)0 (de Wolff, 1974;Stokes et al., 2011;van Smaalen et al., 2013) and found to be essentially associated with small modulation of translation and rotation (ω) normal to the mean molecular plane, and a significant torsion (ϕ) between the phenyl rings (Baudour & Sanquer, 1983;Petricek et al., 1985;Pinheiro & Abakumov, 2015;Schoenleber, 2011).Theoretical studies have suggested that competition between intramolecular and intermolecular forces drives the phase transition towards the incommensurately modulated states (Ishibashi, 1981;Benkert et al., 1987;Benkert & Heine, 1987;Parlinski et al., 1989).
The fundamental property of flexibility in conformations have made biphenyl an excellent candidate to tune in multifaceted properties in materials.Torsion between the rings has been demonstrated to regulate conductivity of single molecule biphenyldithiol junctions (Vonlanthen et al., 2009;Mishchenko et al., 2010;Buerkle et al., IUCr macros version 2.1.15:2021/03/05 2012; Jeong et al., 2020), tune in thermopower as function of twist angle (Buerkle et al., 2012), degeneracy of energy states on substrates (Cranney et al., 2007) and theoretically suggest wide band gap semiconducting properties of its derivatives (Khatua et al., 2020).On the other hand, biphenyl derivatives have also been reported to influence and increase the efficiency of photophysical properties (Oniwa et al., 2013;Wei et al., 2016).Planar biphenyl molecule in solid state favours maximum intramolecular conjugation of π electrons as well as increases the probability of interactions between delocalized electrons that could aid in optimal stacking of molecules.Coupling reaction mechanism (Seechurn et al., 2012) was successfully employed to synthesize 4-biphenylcarboxy protected amino acid esters of L-serine, L-tyrosine, L-alanine, L-leucine and L-phenylalanine (Sasmal et al., 2019b;Sasmal et al., 2019a).In solid state, the compounds crystallize either in acentric orthorhombic space group symmetry P 2 1 2 1 2 1 or the monoclinic subgroup P 2 1 (Sasmal et al., 2019b;Sasmal et al., 2019a).
Crystal packing in these systems is determined by π•••π stacking between the biphenyl fragments and linear strong hydrogen bonds between the amino acid ester moieties.
We presumed that the biphenyl moieties in these chemically coupled systems could influence the bioactive amino acid esters and vice-versa with respect to evolution or suppression of translational and rotational degrees of freedom in their crystal structures at some thermodynamic condition.Reanalyzing all their crystal structures, the system of 4-biphenylcarboxy-(L)-phenylalaninate attracted our attention because the structure appeared to be similar to the L-tyrosine analogue albeit the monoclinic distortion (Table 1, (Sasmal et al., 2019a)) and two crystallographically independent formula units [Z = 2 (Steed & Steed, 2015), Fig. 4(a)] in the crystal structure of the former.The torsion about the chiral center is significantly different for the independent molecules while the rest of the rotations are similar [Fig. 4(a), (Sasmal et al., 2019a)].
In the present study, T -dependent phase transition of 4-biphenylcarboxy-(L)-phenylalaninate has been investigated using single crystal X-ray diffraction experiments.The low temperature phase II is found to be a 2a×b×2c superstructure of the high temperature (phase I) structure.The superstructure is described within the (3 + 1)D superspace approach as a commensurately modulated structure (de Wolff, 1974;Janner & Janssen, 1977;Wagner & Schoenleber, 2009;van Smaalen, 2012;Janssen et al., 2018).
Structural properties of the phase I and the modulated structure have been tabulated and compiled within t-plots (t = phase of the modulation).The origin and stability of phase II is discussed in terms of intra-and intermolecular HC•••CH contacts and intermolecular hydrogen bonds and plausible mechanism of the phase transition is suggested.

Temperature dependent single crystal X-ray diffraction
Single crystals of the compound used in this study were obtained from those reported by (Sasmal et al., 2019a).The crystals were protected in oil under mild refrigeration.nificantly higher than that of molecular biphenyl (T c,biphenyl = 42 K).On the other hand, related polyphenyls p-terphenyl and p-quarterphenyl undergo phase transition towards superstructure phases at much higher critical temperatures (T c,terphenyl ≈ 190 K (Yamamura et al., 1998), T c,quarterphenyl ≈ 233 K (Saito et al., 1985)).Complete diffraction data were collected at T = 160 K and T = 100 K respectively.
Determination of lattice parameters and data reductions were performed using the software suite CrysAlisPro (Cry, 2019) (Table 1, Table S1 in supporting information).Satellite reflections of first order (m = 1) observed below T c could be indexed with modulation wave-vector q = (σ 1 ,0,σ 3 ), σ 1 = σ 3 1 2 with respect to the basic monoclinic lattice.Here, the q = 1 2 (101) is perpendicular to the b axis consistent with monoclinic symmetry while in molecular biphenyl q I violates monoclinic symmetry and q II is parallel to b (Cailleau et al., 1978).Using the plugin program NADA (Schoenleber et al., 2001) in CrysAlisPro, deviation of the σ's as function of T from a rational value of 0.5 were found to be within their e.s.ds (Table 1), indicating a commensurate nature of the modulation.Reflections at T = 100 K were indexed by four integers (hklm) using a basic monoclinic b-unique lattice (Table 1, Table S1 in supporting information) and modulation wave vector, q = ( 1 2 ,0, 1 2 ) and data integration was performed.Empirical absorption correction was performed using AbsPack program embedded in CrysAlisPro.The monoclinic lattice as well as the reflection conditions suggest the superspace group P 2 1 (σ et al., 2011;van Smaalen et al., 2013).
2.1.1.Structure refinement of the modulated structure The crystal structure of the room temperature phase (phase I hereon) was redetermined at T = 160 K using Superflip (Palatinus & Chapuis, 2007) and refined using Jana2006 (Petricek et al., 2014) and Jana2020 (Petricek et al, 2022).Atoms were renamed with suffixes 'a' IUCr macros version 2.1.15:2021/03/05 and 'b' for the two independent molecules 'A' and 'B ' [Fig. 4(a)].Anisotropic atomic displacement parameters (ADPs) of all non-hydrogens atoms were refined.Hydrogen atoms (H) were added to carbon and nitrogen atoms using riding model in ideal chemical geometry with constraints for isotropic ADPs [U iso (H) = 1.2U eq (N), U iso (H) = 1.2U eq (C aromatic ) and U iso (H) = 1.5U eq (C sp3 )].Since β is close to 90 deg, the integrated data was tested for twinning employing twofold rotation parallel a as twin law.This twin law is a true symmetry element in case of a hypothetical orthorhombic lattice with point group symmetry 222 (Petricek et al., 2016;Nespolo, 2019).The fit of the structure model improved (compare R obs F = 0.0463 to 0.0408) and volume of the second component refined to ∼ 2% (Table S2 in supporting information).Finally, positions of the H atoms of NH groups and parameter corresponding to isotropic extinction correction was refined that further improved R obs F values (= 0.0393, Table S2 in  The modulated structure of phase II at T = 100 K was refined using Jana2006 and Jana2020.Fractional co-ordinates of all non-hydrogen atoms from the crystal structure at T = 160 K were used as starting model and the average structure was refined against main reflections.In successive steps, an incommensurate (IC) model described by one harmonic wave for displacive modulation describing the atomic modulation functions (AMFs) and basic parameters for anisotropic ADPs for all atoms was refined against main and satellite reflections that resulted in good fit to the diffraction pattern (R obs F = 0.0425).However, ADPs of four non-hydrogen atoms were found IUCr macros version 2.1.15:2021/03/05 to be non-positive definite.Since the components of q, σ 1 and σ 3 are rational, three commensurately modulated structures were pursued by fixing the initial phase of the modulation to values, t 0 = 0,  S2 in supporting information).

Structural phase transition and unequal distortion of molecules
In the present case, the monoclinic symmetry is retained below T c unlike monoclinic to triclinic distortion at disorder-order phase transition of p-terphenyl (Rice et al., 2013) and p-quarterphenyl (Baudour et al., 1978).In the final commensurately modulated structure model with t 0 = 1 4 , sections corresponding to t = 1 4 and 3 4 (Fig. 4, and 'B' of phase I (Fig. 4).The covalent bond distances are similar for the independent set of molecules and are practically unaffected by modulation (Table S6 in supporting information).In the present study, discussion is based on the modulated structure in order to establish unique relations between phase I and II respectively (Rekis et al., 2021;Ramakrishnan et al., 2019;Dey et al., 2016;Noohinejad et al., 2015;Schoenleber, 2011;Schoenleber et al., 2003).
The modulated structure suggests that the phase transition is dominated by evolution of internal torsional degrees of freedom (ϕ 3 > 0 • ) within the biphenyl moieties where the maximum amplitude are along b for the carbon atoms of biphenyl (Fig. 4 and Table S4 in supporting information).Notably, the rotations in the present structure are significantly larger than those reported for molecular biphenyl [ϕ ± 5.5 deg in ref. (Petricek et al., 1985;Baudour & Sanquer, 1983;Baudour & Sanquer, 1983)] but smaller than those in the low temperature superstructure of p-terphenyl and pquarterphenyl [Maximum ϕ terphenyl,quarterphenyl 23 deg in ref. (Rice et al., 2013;Baudour et al., 1976;Baudour et al., 1978)].Another distinctive property of the modulated structure is the unequal modulation for the two different moieties where u biphenyl > u phenylalaninate (Table S4 in supporting information).Therefore, the variation in torsions ϕ 1 and ψ are smaller [Fig.(C13, C17, C20, C22) positions are strongly displaced (Fig. 4, Table S4 and S5 in supporting information).Subsequently, the ADPs are significantly reduced as compared to phase I (Fig. 4, Table S5 in supporting information).Notably, decrease of the ADPs (U eq ) from T = 160 K to T = 100 K is larger for those of molecule 'A' than those for 'B', while the square of the amplitude of modulations (u 2 ) are greater for 'A' than those for 'B' [compare Fig. 4(b) to Fig. 4(a)].

Competitive forces governing modulations
Structural studies in the 3D phase of molecular biphenyl have suggested that the ortho-hydrogen atoms are displaced away in the plane of the rings to minimize steric hindrance (Trotter, 1961;Hargreaves & Rizvi, 1962;Charbonneau & Delugeard, 1976).
On the other hand, dynamic disorder predominantly governed by torsional vibrations around the long molecular axis (Petricek et al., 1985) is predicted to balance the planar conformation of biphenyl favourable for crystal packing (Lenstra et al., 1994).As short as 1.98 Å in phase I (Table 2), these contacts are shorter than the predicted values for twice van der Waals radius for hydrogen (r = 1.1-1.2Å (Rowland & Taylor, 1996;Alvarez, 2013)).In the modulated structure, we observe that the distances between the ortho-hydrogen atoms are marginally but consistently larger than those in phase I (Table 2) that could suggest that the torsional modulations aid in minimization of the presumed steric hindrance below T c (Dey et al., 2022;Dey et al., 2018).
A peculiar property of the modulated structure under discussion is the significant difference in the torsional amplitude ϕ 3 of the independent molecules.This aspect cannot be explained solely based on the intramolecular steric factors.Analysis of the crystal packing shows that each of these independent biphenyl moieties maintains close intermolecular CH•••HC contacts with the phenyl rings of L-phenylalaninate in AB and BA fashion (Fig. 4).These distances are significantly longer (intermolecular

Conclusions
The single crystal to single crystal phase transition of 4-biphenylcarboxy-(L)-phenylalaninate below T = 124 K drives the 3D structure directly to a locked-in twofold superstructure.The commensurately modulated structure at T = 100 K is accompanied by pronounced amplitudes of torsion within biphenyl that are characteristic of modulated and superstructures of other polyphenyls.The phase transition temperature is significantly higher than that in biphenyl yet significantly smaller than for p-terphenyl and pquarterphenyl.Consistent with the T c , the maximum amplitude of torsion is also inter- independent molecules which is governed by multiple level of competitions involving unequal van der Waals constraints in presence of weak hydrogen bonds between the biphenyl and L-phenylalaninate moieties.The unusual nature of the phase transition is described by the fact that unequal displacive modulations of the two molecules are complimented by unequal suppression of the dynamic disorder of their atoms below T c .This difference in the torsion as well as the phase transition conditions highlights how conjugation of polyphenyls can possibly be influenced by amino acid esters which in turn influences supramolecular assemblies.

Details of structure refinements of different modulated structure models
Structure refinements have been performed using Jana2006 1 and Jana2020 2 .Structural model at T = 160 K has been used as an initial model for the basic structure of the modulated structure at T = 100 K.All atoms were set to isotropic for displacement parameters and the model was refined against main reflections [R obs F (m=0) = 0.0723].In the next step, first order harmonic for displacive modulation was described for all atoms and an incommensurate (IC) model was refined against main and satellite reflections.Refinement led to improved fit to the main reflections [R obs F (m=0) = 0.0586, R obs F (m=1) = 0.1215].Refinement of the anisotropic atomic displacement parameters (ADPs) of all non-hydrogen atoms resulted in significant improvement to the residual values [IC model A: R obs F (m=0) = 0.0374, R obs F (m=1) = 0.0771] and residual features (∆ρ min /∆ρ max ) decreased from -0.68/1.23 e Å−3 to -0.33/0.31e Å−3 .However, ADPs of four non-hydrogen atoms were found to be non-positive definite.Further test by describing first order harmonic for ADP modulation for all non-hydrogen atoms model led to improvement of the residual values [IC model A: R obs F (m=0) = 0.0363, R obs F (m=1) = 0.0677] but ADPs of 11 non-hydrogen atoms were found to be non-positive definite along certain t-sections.This model was discarded for further analysis.
In the next step, IC model A was used as a starting model to describe three commensurate (C) models by fixing the initial phase of the modulation, t 0 = 0, 1  4 and 1 8 respectively.The former two t 0 values correspond to 2a × b × 2c superstructure in 3D with monoclinic symmetry B2 1 while the later correspond to a superstructure with triclinic B1 symmetry.Restrictions on t 0 values also impose constraints on the refinable variables corresponding to atomic modulation functions (AMFs).These restrictions follow the argument that the total number of refinable parameters in the equivalent 3D superstructure and their (3+1)D commensurately modulated structural models must be equal.In the present case, either sin or cos waves can be refined for structural models with t 0 = 0 and 1 4 because the point group symmetry is same in their corresponding 3D superstructure models.On the other hand, assumed monoclinic to triclinic distortion in the 3D superstructure (space group B1)corresponding to (3+1)D C model with t 0 = 1 8 can be derived by using both components of the Fourier series.It must be noted that such restrictions on sin and cos waves cannot be formally imposed on the AMFs of hydrogen atoms in Jana2006 and Jana2020 as their modulations are fully determined by geometrical conditions of the riding model.t 0 = 1 4 yielded the best fit to the diffraction data (Table S3) with reduced number of parameters as compared to the IC model A (compare N C,t 0 =0.25 = 649 to N IC,model A = 811).Most importantly, ADPs of all non-hydrogen atoms are positive definite.
Notably, the residual values of the IC model as well as the C model at t 0 = 1 8 is marginally No.
superspace suggest multiple competing factors involving intramolecular steric factors, intermolecular H-C•••C-H contacts and weak C-H•••O hydrogen bonds that govern the distinctively unequal torsional property of the molecules.1. Introduction Molecular biphenyl has been investigated extensively for its stability and conformation in different thermodynamic states.At ambient conditions, the differences in the conjugation states of the π-electrons are governed primarily by the twist about the central C-C single bond in the order: 40 deg -45 deg in gas phase, 20 deg -25 deg in solution and 0 deg (mutually coplanar) in the solid state in centrosymmetric monoclinic space group P 2 1 /a supporting information).The crystal structure reproduced the values for intramolecular rotations reported those for the structure at T = 200 K [ϕ chiral = ϕ 1 (hereon) and ψ in Fig.4(a)].In addition, we also observe that the coplanar biphenyl rings are significantly rotated with respect to the amide groups [at T = 200 K: ϕ 2 = 32.8deg and 31.2 deg(Sasmal et al., 2019a), at T = 160 K in Fig.4(a)] which also remains invariant as function of temperature.

1 4 and 1 8
respectively.While the former two t 0 values describe monoclinic B2 1 space group symmetry for the equivalent 3D 2a × b × 2c superstructure, the third corresponds to triclinic B1 symmetry.The commensurately modulated structure (C) model corresponding to t 0 = 1 4 resulted in the best fit to the diffraction data (R obs F = 0.0426) including ADPs of all atoms positive definite.As the atomic modulation functions (AMFs) have sinusoidal character, the residual values are similar to the IC model (Fig. 4, Fig. S2-S4 and Table S2 in supporting information) However, the C model at t 0 = 1 4 is described with either cosine or sine waves for the AMFs (equal to number of refinable fractional coordinates in the equivalent superstructure) reducing significantly the number of refinable parameters as compared to the IC model (compare N C = 649 to N IC = 811, further tests in supporting information).The final C model was further improved by refining the parameter corresponding to isotropic extinction correction and AMFs and positions of hydrogen atoms of NH groups (R obs F = 0.0419, Table

Fig
Fig. S5 in supporting information) are physically relevant that corresponds to atomic positions in the equivalent twofold superstructure in 3D (Fig. 4, Fig. S6 in supporting information).Crystal structures of phase I and phase II have group-subgroup rela-

[
Fig. 4(a)].The twists about the central C-C bond are significantly different for the two molecules where the torsional modulation of 'A' are 2-4 times larger than those of 'B' (dihedral angle: | ϕ 3 A | = 15.6 deg, 20.5 deg; | ϕ 3 B | = 4.1 deg, 9.3 deg).These torsions are described by highly anisotropic AMFs (u) along the three basis vectors 4(c),(d)].A possible reason for the weaker modulations of the atoms around the chiral centers is the directional strong intermolecular N-IUCr macros version 2.1.15:2021/03/05 H•••O bonds makes large intramolecular rotations unfavorable.Note that the observed changes in the rotations ϕ 2 [Fig.4(b)] of molecule 'A' are predominantly described by strong modulations of the molecule's biphenyl moiety.The asymmetry in rotations of individual molecules (∆ | ϕ 3 | ≈ 5 deg) is determined by the disparate bonding environments of the biphenyl moieties where the inner rings are that are covalently bonded to amide groups while the outer interact weakly via C-H•••H-C interactions with the phenyl rings of phenylalaninate groups (Fig. 4).Subsequently, the unequal values at the relevant t-sections of ϕ 3 are correlated to those of ϕ 2 [compare Fig. 4(a) and Fig. 4(b)] suggesting the chemical influence of the amide groups on the phenyl rings and vice-versa.In the modulated structure, the biphenyl moieties in (AA) n and (BB) n stacks are tilted with respect to each other [Fig.4(e)] which are parallel in phase I.These tilts (θ AA/BB ) are of the order of the internal twists, ϕ 3 of the independent biphenyl moieties [compare Fig. 4(e) to Fig. 4(a)] The orientation between the biphenyl moieties within the (ABAB) n stacks also vary with ∆θ AA/BB 12 deg where the value is intermediate to ϕ 3 A and ϕ 3 B [compare Fig. 4(e) to Fig. 4(a)].In addition, intermolecular distances between the biphenyl moieties within the stacks at the two t-sections are different and vary up to ∆d AA/BB 0.05 Åand ∆d ABAB 0.02 Å[Fig.4(f)].However, these variations in d are small compared to the molecular tilts, θ.It could therefore be argued that the dimerization of biphenyl molecular stacks below T c are predominantly governed by distortion described by molecular rotations rather than intermolecular distances.On the other hand, intermolecular distances between aromatic rings of Lphenylalaninate vary similarly to the biphenyls albeit significantly smaller interstack rotations, θ < 3 deg (Fig. S5 in supporting information).The increased distortions are also accompanied by suppression of dynamic disorder below T c .For example, the carbon atoms at ortho (C14, C16, C19, C23) and meta IUCr macros version 2.1.15:2021/03/05 mediate and in the order ϕ quarterphenyl ≥ ϕ terphenyl > ϕ 4−biphenylcarboxy−L−phenylalaninate > ϕ biphenyl .Topologically separated, conformations of both the weaker C-H•••O bonds and stronger N-H•••O bonds are rigid and that underlines their role in stabilizing the crystal packing in both phases.A unique property of the present polyphenyl coupled amino acid ester is the distinctively unequal torsional amplitude (ϕ A > ϕ B ) within the IUCr macros version 2.1.15:2021/03/05

Figure S1 :
Figure S1: Diffraction images across the normal (phase I) to commensurately modulated (phase II) phase transition.Red arrows depict Bragg peaks in phase I and main Bragg peaks in phase II.The satellites are diffuse at T = 124 K (green arrow) that becomes stronger at lower temperatures.Reflections at T = 126 K are indexed using three integers (hkl) and at T c = 124 K and lower temperatures by four integers (hklm), where m = 0 and m = 1 for main and satellite reflections respectively.Image resolution range in d ∼ 2.2 to 1.1 Å.

Figure S2 :
Figure S2: (x si ,x s4 )-sections of Fourier map centered on nitrogen atoms (light blue) of amide groups (a) atom N1a of molecule 'A' and (b) atom N1b of molecule 'B'.The contour line and the width of the maps are 0.5 e Å−3 and 2.5 Å respectively.

FigureFigureFigure
Figure S3: (x si ,x s4 )-sections of Fourier map centered on carbon atoms (black) (a) C8a of molecule 'A' and (b) C8b of molecule 'B' respectively belonging to the phenyl ring of Lphenylalaninate moieties.The contour line and the width of the maps are 0.5 e Å−3 and 2.5 Å respectively.

Figure S7 :
Figure S7: Comparison of fit of the experimental powder X-ray diffraction pattern to (a) as obtained unit cell from SCXRD, (b) Calculated unit cell 1 with volume 1901 Å3 and (c) calculated unit cell with volume 2029 Å3 .Experimental pattern, calculated profile and difference are given in black cross points, red curve and black curve respectively.The insets in 2θ = 7-20 deg are given in the right column corresponding to the area (dashed rectrangle) in left.

Table 2 )
H•••H ≥ 2.4 Å, Table2) compared to the intramolecular H•••H distances.On the other hand, the aromatic rings of L-phenylalaninate interact with adjacent oxygen atoms .We argue that in the presence of both the van der IUCr macros version 2.1.15:2021/03/05 d Waals interactions and weak C-H•••O bonds, the larger distortions of 'A' is favored by weaker CH•••HC interactions while that is suppressed in 'B'.The four different values of intramolecular torsion ϕ 3 within the biphenyl moieties is distinctively governed by intra-and intermolecular non-bonded H•••H contacts as well as weak hydrogen bonds.

Table S3 :
Statistical parameters (R obs F , wR all F 2 ) of the (3+1)D incommensurately modulated (IC) and commensurately modulated (C) refinements of models with different values of the phase t 0 .Number of reflections (obs/all) used in the refinements are averaged for the lowest triclinic point group symmetry: (m=0) = 4911/5241, (m=11) = 2031/5537.Space group (SG) symmetries of the equivalent 3D superstructures corresponding to different C structures are given which for the IC structure is meaningless.

Table S4 :
Components of the amplitude of atomic modulation functions (|u x |, |u y | and |u z |) along the three basis vectors a, b and c respectively for molecules A and B.

Table S6 :
Comparison of interatomic bond distances ( Å) of molecules A and B in phase I (T = 160 K) and phase II (T = 100 K).

Table S7 :
Comparison of lattice parameters and residual values from Le baile fit of the PXRD pattern based on two unit cells.Lattice parameters obtained from SCXRD data has been given as reference.