Exploring crystal, electronic, optical and NLO properties of ethyl 4-(3,4-dimethoxy phenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro pyrimidine-5-carboxylate (MTTHPC)

Both theoretical and experimental studies are briefly discussed to shed lights on crystal shape, FT-IR, electronic, and non-linear opto-response (NLO) characteristics of ethyl4-(3,4-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (MTTHPC). Theoretical FT_IR results are in a proper concord with recorded measurements. MTTHPC has TDM (4.78 Debye) and a doublet spins that splits original FMOs into alpha↑,2.44eV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$alpha\left( { \uparrow ,~\;2.44\,{\text{eV}}} \right)$$\end{document} and beta\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$beta$$\end{document}(↓, 1.28 eV) offsets, respectively. MTTHPC is a potential competitor for finest perovskite solar cells (MAPbI3/Au-nanospheres) that possess a band offset (3.1eV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$3.1\,{\text{eV}}$$\end{document}) with conversion-efficiency 24.84%. MTTHPC may be the next chapter for unique avalanche photodetectors (APD). MTTHPC 1st order hyperpolarizability is 14.15∗10-30esu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$14.15*~10^{{ - 30~}} \,{\text{esu}}$$\end{document}, surpass reference urea (≈40βurea,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$( \approx 40\beta _{{urea}} ,$$\end{document}βurea=0.3728∗10-30esu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\beta _{{urea}} = ~0.3728*~10^{{ - 30}} \,{\text{esu}}$$\end{document}). Briefly, MTTHPC may be admitted as the next stage in forthcoming NLO technology.


Mulliken charges and frontiers molecular orbital (FMOs) analyses
Mulliken atomic charges(Q) play a vital role in describing electro negativity, charge transport during a chemical process and overall electronic configuration of the molecule (Guidara et al. 2014). The calculated Mulliken distributions of MTTHPC charges are listed at Table 3. Figure 3 shows  Table 4 for MTTHPC. The E LUMO∕HOMO offset is a precise index for electron carry via conduction domain (Sheela et al. 2015;Verma et al. 2021;Dwivedi, Kumar 2021). The MTTHPC has TDM (4.78 Debye) and a doublet spins that splits original FMOs into alpha(↑) and beta (↓) offsets with energies 2.44 and 1.28 eV, respectively. Which predicts that increasing dipole moment state will increase optical nonlinearity. In a logic way, MTTHPC is a potential competitor for finest perovskite solar cells (MAPbI 3 ) embedded with Au nanospheres that possess a band offset (3.1 eV) with conversion-efficiency 24.84% (Tabrizi et al. 2021). Figures 4 and 5 show computed band offsets and electronic density of states (DOS) for MTTHPC, respectively. Obviously, doublet spins drag Fermi level up to 566 β C-O + β C-S + β C-N + β C-C 15 516 521 γ C-O + γ C-S + γ C-N + γ C-C conduction domain that increase electrons avalanche percent. Hereby, authors declare that MTTHPC may be the next chapter for unique avalanche photodetectors (APD).

NLO Properties
To inspect MTTHPC NLO response, its polarizability and 1st hyperpolarizability are determined via WB97XD_6-311G (d,p). Static_polarizability (α tot ), polarizability_anisotropy ( Δ ) and 1st hyperpolarizability ( tot ) are derived via assorted formulas (Kosar et al. 2021;Yousif 2021): NLO response depend upon associated TDM, α tot and β tot values. MTTHPC calculated results for α tot , Δα and β tot are listed in Table 5. Results are transmuted from SI ⇒ esu scale ; 1 a.u = 0.1482 * 10 −24 esu, ; 1 a.u = 8.6393 * 10 −33 esu . MTTHPC has tot is 14.15 * 10 -30 esu, which is a significant increase above related compounds (Shavel et al. 2004;Bouchouit et al.2008;Guezguez et al. 2013Guezguez et al. , 2014. Such behavior is induced by electrons rush across crystal that cause 1st hyperpolarizability to be doubled over conventional prototype. The close resemblance between NLO value and our finding supports the notion that POM's electro-optic effect is mostly of electronic origin (Dou et al.1993). The observation has been discussed in a variety of organic molecular crystals (Stevenson et al. 1973;Stevenson et al. 1973;Garito et al. 1980), and it appears to be a property shared by those molecules. Within the 0.5-2.0 µm transparency region, many organic compounds exhibit higher nonlinear optical susceptibilities than most inorganics (Morrell et al.1979). The disparity between an experimental POM's NLO and that predicted by theory (most

Fig. 2 Observed and theoretical IR charts for MTTHPC
found in organic crystals) can be utilized as a crystal quality criterion (Zyss et al.1981;Dou et al. 1991Dou et al. , 1992

Pharmaco-kinetics and drug-like nature
Swiss-ADME online-software (Rana et al. 2021; Alshammari 2020) is utilized to predict pharmaceutical features such as physicochemicals, pharmacokinetics, lipophilicity,  Table 6. Presence of tetrahydro-pyrimidine moiety in MTTHPC provides antimicrobial activity (Makvandi et al. 2020). Bioavailability Radar (Mishra et al. 2019) is displayed via pre-six physico-chemical indices, namely lipophilia scale, polarity, solubility, edibility, and saturation (see Fig. 6a). All predicted values acknowledge MTTHPC as a promising druglike carriers. Target classes for MTTHPC molecule with ligand protein interactions are represented in Fig. 6b. MTTHPC polar surface area is 100.91 A 2 that shows a high gastrointestinal (GI) absorption and bioavailability (55%). MTTHPC blood-brain barrier (BBB) is nil that indicates a highly hydrophilic-polar drug-nature to predict intestinal permeation

Conclusion
MTTHPC crystal data, FT-IR, electronic and NLO response is fulfilled via DFT model. Optimized structure, IR, and band offsets are calculated using B3LYP level whereas NLO indices are computed through WB97XD. The good agreement between experimental and theoretical FT-IR confirms calculations precision level. The electronegativity, charge transit during a chemical process, and the molecule's overall electronic configuration are all detected using Mulliken atomic charges analysis. MTTHPC possesses a TDM (4.78 Debye) and a doublet-spin offsets, namely alpha (↑, 2.44 eV) and beta (↓, 1.28 eV) . Such doublet-spins drag push Fermi level nearby conduction domain facilitating electrons rush across. So, MTTHPC is a promising candidate for premier avalanche photodetectors as well as solar cells. Also, MTTHPC exhibits a magnificent NLO response, tot is 14.15 * 10 -30 esu, which is a significant increase surpass other relatives. Such behavior is induced by electrons rush across crystal that cause 1 st hyperpolarizability to be doubled over ordinary prototype. Intellectually, MTTHPC may be the next stage in forthcoming NLO technology. Moreover, pharmaceutical features for MTTHPC show its eligibility as efficient drug-carriers for gastrointestinal diseases.