A comprehensive experimental and theoretical investigation of sarcosinium tartrate (C3H8NO2+·C4H5O6−), a proton-transfer molecular salt is presented in this study. Single crystals of sarcosinium tartrate (SRT) were successfully grown by the slow evaporation technique yielding optically transparent crystals with dimensions of approximately 23 × 11 × 6 mm3 and structure was characterized by single-crystal X-ray diffraction, confirming a triclinic crystal system with a non-centrosymmetric arrangement <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$P1$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>P</mi> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> space group. Vibrational analysis performed through FTIR spectroscopy, supported by DFT calculations at the B3LYP/6–311 + + G (d, p) level, showed excellent agreement, validating the molecular structure and functional group assignments. UV–vis–NIR spectrum revealed high optical transparency (~ 96%) in the visible region with a cut-off wavelength at 244 nm and direct optical bandgap of 5.51 eV. Time-dependent DFT (TD-DFT) analysis confirmed that the observed electronic transitions are predominantly governed by HOMO–LUMO charge transfer mechanisms. Frontier molecular orbital analysis revealed a HOMO–LUMO energy gap of 2.098 eV and global reactivity descriptors suggest a balanced combination of stability and reactivity. The second-harmonic generation efficiency was measured using the Kurtz–Perry powder technique with a Q-switched Nd: YAG laser operating at 1064 nm was found to be 3.7 times higher than that of KDP. Laser damage threshold studies performed under nanosecond Nd: YAG laser irradiation demonstrated good resistance to optical breakdown, indicating suitability for high-power photonic applications. The calculated first hyperpolarizability is five times greater than that of urea, demonstrates significant nonlinear optical (NLO) response, highlighting the potential of SRT for second-order NLO applications. Molecular electrostatic potential mapping and Hirshfeld surface analysis further reveal strong intermolecular interactions dominated by O–H···O and N–H···O hydrogen bonds. Crystal void analysis confirms dense packing and mechanical stability.

Integrated experimental and theoretical investigation of sarcosinium tartrate: a promising laser-resistant and nonlinear optical crystal

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发表日期：

2026年7月8日

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S. Vaishnavi,
A. Suvitha,
Nouf Alharbi,
T. Arumanayagam

摘要

A comprehensive experimental and theoretical investigation of sarcosinium tartrate (C₃H₈NO₂⁺·C₄H₅O₆⁻), a proton-transfer molecular salt is presented in this study. Single crystals of sarcosinium tartrate (SRT) were successfully grown by the slow evaporation technique yielding optically transparent crystals with dimensions of approximately 23 × 11 × 6 mm³ and structure was characterized by single-crystal X-ray diffraction, confirming a triclinic crystal system with a non-centrosymmetric arrangement $P1$ $P 1$ space group. Vibrational analysis performed through FTIR spectroscopy, supported by DFT calculations at the B3LYP/6–311 + + G (d, p) level, showed excellent agreement, validating the molecular structure and functional group assignments. UV–vis–NIR spectrum revealed high optical transparency (~ 96%) in the visible region with a cut-off wavelength at 244 nm and direct optical bandgap of 5.51 eV. Time-dependent DFT (TD-DFT) analysis confirmed that the observed electronic transitions are predominantly governed by HOMO–LUMO charge transfer mechanisms. Frontier molecular orbital analysis revealed a HOMO–LUMO energy gap of 2.098 eV and global reactivity descriptors suggest a balanced combination of stability and reactivity. The second-harmonic generation efficiency was measured using the Kurtz–Perry powder technique with a Q-switched Nd: YAG laser operating at 1064 nm was found to be 3.7 times higher than that of KDP. Laser damage threshold studies performed under nanosecond Nd: YAG laser irradiation demonstrated good resistance to optical breakdown, indicating suitability for high-power photonic applications. The calculated first hyperpolarizability is five times greater than that of urea, demonstrates significant nonlinear optical (NLO) response, highlighting the potential of SRT for second-order NLO applications. Molecular electrostatic potential mapping and Hirshfeld surface analysis further reveal strong intermolecular interactions dominated by O–H···O and N–H···O hydrogen bonds. Crystal void analysis confirms dense packing and mechanical stability.