Screening for cocrystals¶

In this section, we provide an example application that can be used as a template for many high-throughput screening scripts. Cocrystals are crystals formed from two or more compounds in a defined stoichiometry. There are many uses for cocrystals, especially for pharmaceutical applications where one compound is an active pharmaceutical ingredient (API). This example problem screens multiple compounds for their potential as components of a (1:2) cocrystal with Itraconazole. This problem uses the excess enthalpy for a hypothetical supercooled liquid phase as a proxy for cocrystallization affinity. The rankings of the solvents are in good agreement with model and experimental results for this problem given in [1] .

Python code¶

[show/hide code]
import os
import matplotlib.pyplot as plt
from scm.plams import *

##################  Note: Be sure to add the path to your own AMSCRS directory here  ##################
database_path = os.getcwd()

if not os.path.exists(database_path):
raise OSError(f'The provided path does not exist. Exiting.')

init()
#suppress plams output
config.log.stdout = 0

# temperature
sys_temp   = 298.15 # K

# the solute we are trying to find a co-crystal for (Itraconazole)
solute =  ["itz_1.coskf"]

# a list of different conformers for the screening
# each line contains 3 conformers of the same molecule
solv_list=[
["tartaric_acid_1.coskf","tartaric_acid_2.coskf","tartaric_acid_3.coskf"],
["fumaric_acid_1.coskf","fumaric_acid_2.coskf","fumaric_acid_3.coskf"],
["succinic_acid_1.coskf","succinic_acid_2.coskf","succinic_acid_3.coskf"],
["malic_acid_1.coskf","malic_acid_2.coskf","malic_acid_3.coskf"],
["glutaric_acid_1.coskf","glutaric_acid_2.coskf","glutaric_acid_3.coskf"],
["malonic_acid_1.coskf","malonic_acid_2.coskf","malonic_acid_3.coskf"],
["maleic_acid_1.coskf","maleic_acid_2.coskf","maleic_acid_3.coskf"]
]

print("Solvent".ljust(30),"Excess enthalpy (kcal/mol)")
excess_h = []
for solv in solv_list:

name = "_".join(solv[0].split("_")[:-1])

# initialize settings object
settings = Settings()
settings.input.property._h = 'VAPORPRESSURE'

# set the number of compounds
num_compounds = 2
compounds = [Settings() for i in range(num_compounds)]
compounds[0].name = "solvent"

form_s = [Settings() for i in range(len(solv))]
for j in range(len(solv)):
form_s[j]._h = os.path.join( database_path, solv[j] )

compounds[0].form = form_s

compounds[1].name = "Itraconazole"

form_sol = [Settings() for i in range(len(solute))]
for j in range(len(solute)):
form_sol[j]._h = os.path.join( database_path, solute[j] )

compounds[1].form = form_sol
# this is the stoichiometric ratio of the co-crystal
compounds[0].frac1 = 0.33333
compounds[1].frac1 = 0.66667

# to change to the COSMOSAC2013 method
settings.input.method = 'COSMOSAC2013'

#temperature
settings.input.temperature = str(sys_temp)
# specify the compounds as the compounds to be used in the calculation
settings.input.compound = compounds
# create a job that can be run by COSMO-RS
my_job = CRSJob(settings=settings)

out = my_job.run()
res = out.get_results()

excess_h.append((res["excess H"],name))
print (name.ljust(30),round(res["excess H"],5))

plt.xlabel("Excess enthalpy (kcal/mol)")
plt.barh([i for i in range(len(excess_h))],[x[0] for x in excess_h],zorder=3)
plt.yticks([i for i in range(len(excess_h))],[x[1] for x in excess_h])
plt.grid(axis='x',ls="--",zorder=0)
plt.gca().invert_xaxis()

plt.show()

finish()


This figure (produced by the code) shows the excess enthalpy values of all solvents in a supercooled liquid mixture with Itraconazole. The lowest 4 excess enthalpy values correspond to 4 solvent for which a stable co-crystal with Itraconazole is known [1] .

References¶

 [1] (1, 2) Abramov, Yuriy A., Christoph Loschen, and Andreas Klamt. “Rational coformer or solvent selection for pharmaceutical cocrystallization or desolvation.” Journal of pharmaceutical sciences 101.10 (2012): 3687-3697.