03575nas a2200205   4500008004100000022001400041245006600055210006400121260000900185300001200194490000700206520292200213100001903135700002803154700001803182700002103200700002803221700002403249856009603273       2021                        eng d  a1528-748300aCan we identify the salt-cocrystal continuum state using XPS?0 aCan we identify the saltcocrystal continuum state using XPS  cFEB   a735-7470 v213 a<p>X-ray photoelectron spectroscopy (XPS) is used to understand the nature of acid-base crystalline solids, to know whether the product is a salt (proton transfer, O-center dot center dot center dot H-N+) or a cocrystal (neutral adduct, O-H center dot center dot center dot N). The present study was carried out to explore if intermediate states of proton transfer from COOH to nitrogen (the proton resides between hydrogen bonded to O and N, O center dot center dot center dot H center dot center dot center dot N, quasi state) can be differentiated from a salt (complete proton transfer, N+-H center dot center dot center dot center dot O-) and cocrystal (no proton transfer, O-H center dot center dot center dot N) using N 1s XPS spectroscopy. The intermediate states of proton transfer arise when the pK(a) difference between the acid and the conjugate base is between -1 and 4, -1 &lt; Delta pK(a) &lt; 4, a situation common with COOH and pyridine functional groups present in drug molecules and pharmaceutically acceptable coformers. Complexes of pyridine N bases with aromatic COOH molecules in nine salts/cocrystals were cocrystallized, and their N 1s core binding energies in XPS spectra were measured. The proton state was analyzed by single-crystal X-ray diffraction for confirmation. Three new complexes were crystallized and analyzed by XPS spectra (without knowledge of their X-ray structures), to assess the predictive ability of XPS spectra in differentiating salt-cocrystal intermediate states against the extremities. The XPS results were subsequently confirmed by single-crystal X-ray data. Complexes of 3,5-dinitrobenzoic acid and isonicotinamide in 1:1 and 1:2 ratios exist as a salt and a salt-cocrystal continuum, respectively, as shown by the N 1s core binding energies. The proton states of the crystalline solids by XPS are in good agreement with the corresponding crystal structures. Other complexes, such as those of 3,5-dinitrobenzoic acid with 1,2-bis(4-pyridyl)ethylene, exhibit a salt-cocrystal continuum, maleic acids with 1,2-bis(4-pyridyl)ethylene and acridine are salts, 2-hydroxybenzoic acid and acridine is a salt, and the complex of 3,5-dinitrobenzoic acid and 3-hydroxypyridine is a salt and salt-cocrystal continuum, while fumaric acids with 1,2-bis(4-pyridyl)ethylene and acridine are cocrystals. Furthermore, three new acidbase complexes of 3,5-dinitrobenzoic acid with phenazine, 4-hydroxypyridine, and 4-cyanopyridine were studied initially by XPS and then confirmed by X-ray diffraction. In summary, since the N 1s binding energies cluster in a narrow range as cocrystals (398.7-398.9 eV) and salts (400.1-401.1 eV), it is clearly possible to differentiate between cocrystals and salts, but the saltcocrystal continuum values in XPS spectra are clustered in an intermediate range of cocrystals and salts but overlap with those of cocrystal or salt binding energies.</p>
1 aTothadi, Srinu1 aShaikh, Tabrez, Rafique1 aGupta, Sharad1 aDandela, Rambabu1 aVinod, Chathakudath, P.1 aNangia, Ashwini, K.  uhttps://library.ncl.res.in/content/can-we-identify-salt-cocrystal-continuum-state-using-xps01146nas a2200169   4500008004100000022001400041245012000055210006900175260000900244300001400253490000700267520050100274100002000775700002800795700002300823856013000846       2025                        eng d  a1359-734500aContinuous flow solvent-free and catalyst-free mechanochemical production of rhodamine B dyes and their derivatives0 aContinuous flow solventfree and catalystfree mechanochemical pro  cJAN   a2131-21340 v613 a<p>
	In this communication, we have described a simple and efficient, catalyst free and solvent-free protocol for the continuous flow synthesis of rhodamine B dyes developed from 3-diethyl amino phenol and phthalic anhydride. Nearly 95% conversion was achieved within 12 min using a jacketed single screw reactor. This method is further used for the synthesis of six derivatives with 70-84% yield, which can be compared to 85% yield from a 1-hour long batch synthesis involving a catalyst.</p>
1 aPurohit, Mukesh1 aShaikh, Tabrez, Rafique1 aKulkarni, Amol, A.  uhttps://library.ncl.res.in/content/continuous-flow-solvent-free-and-catalyst-free-mechanochemical-production-rhodamine-b-dyes