Asymmetric Unit Research Articles

N-Benzoyl-morpholine-4-carbothioamides: Crystal structures, Hirshfeld surface analysis, and Density functional theory calculations

The current research work describes facile synthesis, single crystal X-ray structures, Hirshfeld surface (HS) analysis, and density functional theory (DFT) calculations of two N-benzoyl-morpholine-4-carbothioamides (NDMC and NMMC). Consequently, the synthesized compounds, C12H12Cl2N2O2S (NDMC) and C13H16N2O2S (NMMC) crystallized in triclinic and monoclinic crystal systems each having respective space groups of P -1 and P 21, with corresponding a = 7.8045 (3) Å, b = 12.8458 (6) Å, c = 13.4946 (7) Å, α = 97.313 (4)°, β = 94.358 (4)°, γ = 93.348 (3)°, Z = 4 and V = 1334.84 (11) Å3 for compound (NDMC). Similarly, for compound (NMMC),a = 7.3322 (2) Å, b = 5.3045 (1) Å, c = 16.3367 (5) Å, α = 90°, β = 94.285 (3)°, γ = 90°, Z = 2 and V = 633.62 (3) Å3. Subsequently, the asymmetric unit of compound (NDMC) contains two molecules, while compound (NMMC) has single molecule. Strong intermolecular NH⋯O, and weaker CH⋯Cl and CH⋯S hydrogen bonds link the molecules of (NDMC) into dimers, enclosing R22(7) and R22(9) ring motifs. Intermolecular CH⋯S, bifurcated NH⋯O and CH⋯O hydrogen bonds, as well as CH⋯π interactions in (NMMC), attach molecules, enclosing R22(7) and R22(14) ring motifs. Furthermore, HS analysis explored, visualized, and quantified the significance of hydrogen bond contacts, and revealed active contributions for the packed crystals encompasses H…H 33.6 % for (NDMC), and 46.6 % for (NMMC), H…S/S…H 17.9 % for (NDMC), and 17.0 % for (NMMC), H…C/C…H 9.0 % for (NDMC), and 19.7 % for (NMMC), H…O/O…H 14.8 % for (NDMC), and 14.3 % for (NMMC), and H…Cl/Cl…H 17.8 % for (NMMC). Hydrogen bonding and van der Waals contacts strongly influence crystal packings of the crystallized compounds. Similarly, evaluation of energy frameworks (electrostatic, dispersion and total energies) indicated stabilization is strongly dominated by dispersion energy contribution in compound (NMMC). Finally, optimum molecular structures of both the compounds (NDMC and NMMC), were related with the experimental ones employing DFT at B3LYP/6–311G**(d,p) level. The most stable optimized conformation was geometrically complementary with the crystal structure. DFT computed frontier molecular energies and isodensities predicted these compounds to exhibit better electron pair acceptance nature than electron pair donor.

4-Fluoro-2-(phenyl-amino)-benzoic acid.

The title compound, C13H10FNO2, was obtained by the reaction of 2-bromo-4-fluoro-benzoic acid with aniline. There are two independent mol-ecules, A and B, in the asymmetric unit, with slight conformational differences: the dihedral angles between the aromatic rings are 55.63 (5) and 52.65 (5)°. Both mol-ecules feature an intra-molecular N-H⋯O hydrogen bond. In the crystal, the mol-ecules are linked by pairwise O-H⋯O hydrogen bonds to form A-B acid-acid dimers and weak C-H⋯F inter-actions further connect the dimers.

Trinuclear nickel (II) string complexes and copper (II) coordination polymer with pyrazine modulated unsymmetrical dipyridylamino ligand: Synthesis, structure and bioactivity properties with molecular docking

The unsymmetrical pyrazine-modulated ligand, N-(pyridine-2-yl)pyrazin-2-amine (Hppza) (1), its 1D straight-chain copper (II) coordination polymer [Cu2(Hppza)2∙(NO3)4]n (2) and trinuclear metal string [Ni3(µ3-ppza)4Cl2] (3) and [Ni3(µ3-ppza)4(NCS)2] (4) complexes have been successfully synthesized and structurally characterized. The free ligand Hppza (1) exhibits anti-syn conformation. In an asymmetric unit of 2, there are two kinds of Cu(II) atoms, both of which have elongated octahedral coordination geometry, and the copper(II) centers are linked by oxygen atoms of one nitrate anion. There are only minor differences in Ni…Ni bond lengths between pyrazine-modulated ligand complexes of [Ni3(μ3-ppza)4×2] (X = Cl− (3), NCS− (4)) and their unmodulated analogs, while the distances between the terminal nickel atoms and the axial ligands 3 and 4 are shorter. The results of magnetic susceptibility measurements showed an antiferromagnetic exchange constant (J) of about J = –199.2 cm–1 for 3 and J = –178.0 cm–1 for 4. The electrochemical properties of nickel strings of Hppza differ significantly from their unmodulated counterparts. The activities of ligands and their metal complexes against various proteins that are AChE (PDB ID: 4M0E), BChE (PDB ID: 5NN0), α-Gly (PDB ID: 1UAS), hCA I (PDB ID: 2CAB), and hCA II (PDB ID: 3DC3) were compared, and then the ADME/T properties of molecules were examined. Afterward, the interactions occurring in the docking calculation were examined in detail with the Protein-Ligand Interaction Profiler (PLIP) service. These complexes were inhibitors of BChE, hCA I and II, α-glycosidase and AChE enzymes for complex 3 and 5 with Ki values of 12.65 and 42.95 μM for hCA I, 3.64 and 15.84 μM for hCA II, 5.44 and 50.07 μM for BChE, 15.85 and 4.77 μM for α-glycosidase and 8.58 and 86.24 μM for AChE, respectively.

Discovery of indoleninyl-pyrazolo[3,4-b]pyridines as potent chemotherapeutic agents against colorectal cancer cells

A new series of indolenines decorated with pyrazolo[3,4-b]pyridines were designed and synthesized in up to 96% yield from the acid-catalyzed cyclocondensation of 1,3-dialdehydes with 3-aminopyrazoles. X-ray crystallography on a representative derivative, 5n, revealed two close to planar conformations whereby the N-atom of the pyridyl residue was syn or anti to the pyrrole-N atom in the two independent molecules of the asymmetric unit. The computational and DNA binding data suggest that 5n is a strong DNA intercalator with the results in agreement with its potent cytotoxicity against two colorectal cancer cell lines (HCT 116 and HT-29). In contrast to doxorubicin, compounds 5k-o have higher druggability (compliance to more criteria stated in Lipinski’s rule of five and Veber’s rule), higher bioavailability, and better medicinal chemistry properties, indicative of their potential application as chemotherapeutical agents.

Prop-2-ynyl 3-meth-oxy-4-(prop-2-yn-yloxy)benzoate.

The title compound, C14H12O4, comprises of two crystallographically independent mol-ecules in the asymmetric unit, linked via C-H⋯O inter-actions to form dimeric entities. The allylic groups are twisted out of the phenyl planes with dihedral angles varying between 7.92 (13) and 25.42 (8)°. In the crystal, the packing follows a zigzag pattern along the c-axis direction. The absolute configuration of the sample could not be determined reliably.

Structural and biophysical characterization of PadR family protein Rv1176c of Mycobacterium tuberculosis H37Rv

Rv1176c of Mycobacterium tuberculosis H37Rv belongs to the PadR-s1 subfamily of the PadR family of protein. Rv1176c forms a stable dimer in solution. Its stability is characterized by a thermal melting transition temperature (Tm) of 39.4 °C. The crystal structure of Rv1176c was determined at a resolution of 2.94 Å, with two monomers in the asymmetric unit. Each monomer has a characteristic N-terminal winged-helix-turn-helix DNA-binding domain. Rv1176c C-terminal is a coiled-coil dimerization domain formed of α-helices α5 to α7. In the Rv1176c dimer, there is domain-swapping of the C-terminal domain in comparison to other PadR homologs. In the dimer, there is a long inter-subunit tunnel in which different ligands can bind. Rv1176c was found to bind to the promoter region of its own gene with high specificity. M. smegmatis MC2 155 genome lacks homolog of Rv1176c. Therefore, it was used as a surrogate to characterize the functional role of Rv1176c. Expression of Rv1176c in M. smegmatis MC2 155 cells imparted enhanced tolerance towards oxidative stress. Rv1176c expressing M. smegmatis MC2 155 cells exhibited enhanced intracellular survival in J774A.1 murine macrophage cells. Overall, our studies demonstrate Rv1176c to be a PadR-s1 subfamily transcription factor that can moderate the effect of oxidative stress.

Crystal structure of the tetra-ethyl-ammonium salt of the non-steroidal anti-inflammatory drug nimesulide (polymorph II).

The crystal structure of the tetra-ethyl-ammonium salt of the non-steroidal anti-inflammatory drug nimesulide (polymorph II) (systematic name: tetra-ethyl-ammonium N-methane-sulfonyl-4-nitro-2-phen-oxy-anilinide), C8H20N+·C13H11N2O5S-, was determined using single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P21/c with one tetra-ethyl-ammonium cation and one nimesulide anion in the asymmetric unit. In the crystal, the ions are linked by C-H⋯N and C-H⋯O hydrogen bonds and C-H⋯π inter-actions. There are differences in the geometry of both the nimesulide anion and the tetra-ethyl-ammonium cation in polymorphs I [Rybczyńska & Sikorski (2023 ▸). Sci. Rep. 13, 17268] and II of the title compound.

Bis[μ-bis-(pyridin-2-yl)methanone oxime-κ3N:,N',N'']bis-[di-acetato-κ2O,O';κO-zinc(II)].

The structure of the title complex, [Zn2(C2H3O2)4(C11H9N3O)2], is triclinic containing half of the mol-ecule in the asymmetric unit. Each zinc atom is coordinated to a pyridyl and oxime nitro-gen from one di-2-pyridyl ketone oxime (dpko) ligand and a third nitro-gen from the other dpko pyridyl ring. Additionally, each zinc is coordinated to two acetato anions, one of which is bidentate and the other monodentate. The uncoordinated oxygen of the monodentate acetato group is involved in a hydrogen bond with the oxime hydrogen. The packing in the crystal is assisted by weak C-H⋯O inter-actions between acetato groups and neighboring pyridyl rings.

A 1D Sb-containing hybrid organic-inorganic material: Synthesis, structural characterization, hirshfeld surface, thermal behavior, vibrational and optical properties

A novel interesting hybrid organic-inorganic material of Bis (2-amino-3-nitropyridinuim) pentachloroantimoinates (III) with the formula [C5H6N3O2]2SbCl5 was elaborated by slow evaporation at room temperature. This compound was crystallized in the monoclinic system with the P 21/c space group, as shown using the X-ray diffraction results. The parameters are the following: a = 16.484(6) Å, b = 7.7170 (19) Å, c = 16.159 (7) Å, β= 109.26(5)°, Z = 4 and V = 1940,5(14) Å3. The asymmetric unit consists of one Sb (III) cation surrounded by five Cl− and two protonated cations 2-amino-3-nitropyridinuim. The crystal packing cohesion was maintained by NH…Cl and NH…O hydrogen bonds to form a three- dimensional network. The infrared IR and Raman studies which were recorded at room temperature in the 4000–400 cm−1 and 0–4000 cm−1 frequency regions, respectively, confirmed the existence of vibrational modes that correspond to the organic and inorganic groups. The Hirshfeld analysis results show that the predominate interactions were H…Cl and O…H contacts (39.9, 14.5 % respectively). The Thermogravimetric analysis TGA shows that this compound remains stable up to about 150 °C. The optical properties were characterized experimentally by UV–visible absorption studies and photoluminescence measurements. The Photoluminescence spectrum manifests a broad and strong band of luminescence around 454 nm (2.73 eV), which can be even observed with the naked eye at room temperature and is due to exciton emission.

A new paddle wheel type Cu(II) complex with photoluminescence and photocatalytic properties

A paddle wheel-shaped complex formulated [Cu2(piv)4(CH3OH)2]·1.5(CH3OH)·0.5(H2O) (1) has been synthesized by a reaction of Cu(NO3)2·3H2O with pivalic acid. The structure of the complex is characterized by FTIR, elemental analysis and single X-ray crystallography. The crystal structure demonstrates that complex exhibits a paddle wheel type configuration. The asymmetric unit of 1 is composed of a half molecule due to the existence of an inversion center between the two Cu(II) centers. The oxygen atoms of the pivalate serve as bridging ligands, and the two methanol molecules occupy the axial position. Each pivalate ion has syn-, syn- coordination mode and its geometry may be described as square pyramidal. The complex works well as a photocatalyst, breaking down methylene blue (MB) by 78.26% after 120 minutes of 30 W ultraviolet light exposure. The optimized photocatalytic parameters were as follows; catalyst loading = 40 mg, primary concentration of MB = 15 mg/L, temperature = 323K, and pH = 8. The reaction kinetics were best demonstrated by a pseudo-first-order kinetic model followed by a rate constant of 0.00715 min–1. The reuse of the catalyst over five photocatalytic runs suggested its excellent sustainability and recyclability. Hydroxyl radicals and superoxide anions were found to be active participants in the catalytic reaction, as investigated by scavenging studies. These findings contributed to a deeper understanding of the mechanistic aspects of the photocatalytic reaction. Theoretical investigation is well support to experimental work.

1-Ethyl-3,3-di-methyl-spiro-[indoline-2,8'-phenaleno[1,9-fg]chromene].

The title pyrene-fused spiro-pyran derivative, C30H25NO, crystallizes with two mol-ecules in the asymmetric unit with dihedral angles between their fused-ring sub units of 76.20 (8) and 89.38 (9)°. In the crystal, weak C-H⋯π inter-actions link the mol-ecules into a three-dimensional network.

Crystal and Molecular Structures of Two Phthalocyanines, Chloro(phthalocyaninato)gallium(III) (ClGaPc) and µ-Oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc)

The structure of µ-oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc) and the structure of a second modification of chloro(phthalocyaninato)gallium(III) (ClGaPc) has been determined by single-crystal X-ray analysis. Sublimation of the respective compounds led to single crystals suitable for an X-ray study. Both compounds crystallize in the triclinic space group P1¯, with a unit cell for ClGaPc a = 13.770 Å, b = 13.770 Å, c = 14.039 Å, α = 98.32°, β = 108.64°, γ = 90.01°, containing four disordered molecules (Z = 4). The unit cell of the dimeric PcGaOGaPc contains one molecule, with half a molecule as an asymmetric moiety (Z = 2) and a = 7.848 Å, b = 12.529 Å, c = 12.720 Å, α = 91.03°, β = 94.94°, γ = 89.98°. The Ga atoms for the two ClGaPc molecules are placed 0.44 Å above the plane formed by the respective isoindole nitrogen N1 to N4. The two rings of the asymmetric unit (molecule 1 and 2) are arranged in parallel, with ca. 3.4 Å distance within the unit cell. The Ga-Cl bond distances are ca. 2.20 Å for the two molecules. The gallium of PcGaOGaPc is placed 0.49 Å above the respective isoindole nitrogen plane and the Ga-O bond amounts to 1.734 Å.

Development of favipiravir dry powders for intranasal delivery: An integrated cocrystal and particle engineering approach via spray freeze drying

The therapeutic potential of pharmaceutical cocrystals in intranasal applications remains largely unexplored despite progressive advancements in cocrystal research. We present the application of spray freeze drying (SFD) in successful fabrication of a favipiravir-pyridinecarboxamide cocrystal nasal powder formulation for potential treatment of broad-spectrum antiviral infections. Preliminary screening via mechanochemistry revealed that favipiravir (FAV) can cocrystallize with isonicotinamide (INA), but not nicotinamide (NCT) and picolinamide (PIC) notwithstanding their structural similarity. The cocrystal formation was characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy, and unit cell determination through Rietveld refinement of powder X-ray analysis. FAV-INA crystalized in a monoclinic space group P21/c with a unit cell volume of 1223.54(3) Å3, accommodating one FAV molecule and one INA molecule in the asymmetric unit. The cocrystal was further reproduced as intranasal dry powders by SFD, of which the morphology, particle size, in vitro drug release, and nasal deposition were assessed. The non-porous flake shaped FAV-INA powders exhibited a mean particle size of 19.79 ± 2.61 μm, rendering its suitability for intranasal delivery. Compared with raw FAV, FAV-INA displayed a 3-fold higher cumulative fraction of drug permeated in Franz diffusion cells at 45 min (p = 0.001). Dose fraction of FAV-INA deposited in the nasal fraction of a customized 3D-printed nasal cast reached over 80 %, whereas the fine particle fraction remained below 6 % at a flow rate of 15 L/min, suggesting high nasal deposition whilst minimal lung deposition. FAV-INA was safe in RPMI 2650 nasal and SH-SY5Y neuroblastoma cells without any in vitro cytotoxicity observed. This study demonstrated that combining the merits of cocrystallization and particle engineering via SFD can propel the development of advanced dry powder formulations for intranasal drug delivery.

Synthesis, characterization, and crystal structures of four 1,3-diisopropylbenzimidazolium salts with iodide, aluminum tetraiodide, tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate, and triiodide anions

Four 1,3-disubstituted benzimidazolium salts: 1,3-diisopropylbenzimidazolium iodide (1), 1,3-diisopropylbenzimidazolium aluminum tetraiodide (2), 1,3-diisopropylbenzimidazolium triiodide (3), and 1,3-diisopropylbenzimidazolium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (4) have been characterized using single X-ray diffraction analysis. Compounds 2–4 are new and are characterized by NMR and IR spectroscopy. Compound 2 was prepared by reacting 1 with aluminum triiodide and compound 4 in a metathesis reaction of 1 with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, giving yields of 96% and 93%, respectively. Compound 3 was prepared by reacting 1 with 1 eq. of iodine and was isolated in 34% yield. Compound 1 crystallizes in the Orthorhombic space group P212121 with an asymmetric unit consisting of one benzimidazolium cation and one iodine anion. Compound 2 crystallizes in the Monoclinic space group P21/ n with an asymmetric unit consisting of one benzimidazolium cation and one aluminum tetraiodide anion. Compound 3 crystallizes in the Monoclinic space group C2/ c with an asymmetric unit consisting of one and one-half benzimidazolium cations and one and one-half triiodide anions. Compound 4 crystallizes in the Triclinic space group P-1 with an asymmetric unit consisting of one benzimidazolium cation and one tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion. The NCN angles in all four compounds are approximately 110°, which is consistent with literature values. Stacking and halogen and hydrogen bonding interactions in the series are also discussed.

Advanced implication theory. Symmetry tables.

The MIF (multiple implication function) group symmetry was assigned to all 230 space groups. Knowledge of MIF symmetry allows the calculation of an asymmetric unit. A more accurate procedure for calculating MIFs has been developed. Extensive tables of MIF symmetry and asymmetric units were computer generated. The development of implication theory for crystal structure determination seems to have reached completion.

[4-(2-Aminoethyl)morpholine-κ2N,N']di-bromidocadmium(II): synthesis, crystal structure and Hirshfeld surface analysis.

The title compound, [CdBr2(C6H14N2O)], was synthesized upon complexation of 4-(2-aminoethyl)morpholine and cadmium(II) bromide tetra-hydrate at 303 K. It crystallizes as a centrosymmetric dimer, with one cadmium atom, two bromine atoms and one N,N'-bidentate 4-(2-aminoethyl)morpholine ligand in the asymmetric unit. The metal atom is six-coordinated and has a distorted octa-hedral geometry. In the crystal, O⋯Cd inter-actions link the dimers into a polymeric double chain and inter-molecular C-H⋯O hydrogen bonds form R 2 2(6) ring motifs. Further C-H⋯Br and N-H⋯Br hydrogen bonds link the components into a three-dimensional network. As the N-H⋯Br hydrogen bonds are shorter than the C-H⋯Br inter-actions, they have a larger effect on the packing. A Hirshfeld surface analysis reveals that the largest contributions to the packing are from H⋯H (46.1%) and Br⋯H/H⋯Br (38.9%) inter-actions with smaller contributions from the O⋯H/H⋯O (4.7%), Br⋯Cd/Cd⋯Br (4.4%), O⋯Cd/Cd⋯O (3.5%), Br⋯Br (1.1%), Cd⋯H/H⋯Cd (0.9%), Br⋯O/O⋯Br (0.3%) and O⋯N/N⋯O (0.1%) contacts.

Embellished photosensitive Schottky barrier diode functionality of Ni(II)/Pb(II)-Salen complex with SCN− spacers: Insights from experimental and theoretical rationalization

This research article explores the synthesizing, structural characterizing, and photosensitive Schottky diode behaviour (PSBD) of one new hetero-nuclear Ni(II)/Pb(II)-Salen complex, [Ni2(L)Pb(μ-1,3-SCN)2(H2O)]2. The complex utilizes various analytical methods for characterization purposes, including single-crystal X-ray diffraction (SCXRD). Crystals have formed in the monoclinic space group P21/n within the compound. The complex asymmetric unit contains a deprotonated ligand (L2−), two Ni(II), one Pb(II), two SCN− ions, and Ni(II) metal coordination by H2O molecule. The crystallographic structure has octahedral and see-saw geometries around the Ni(II) and Pb(II) metal ions. The crystal structure reveals remarkable supramolecular interactions, with significant S⋯H contacts (13 %) evident from the Hirshfeld surface (HS) and 2-D fingerprint plots. The calculated optical band gap (3.14 eV) and UV–Visible measurement support the semiconductor behaviour. In addition, the compound shows electrical conductivity and photosensitivity (dark & light), suggesting potential applications in optoelectronic devices. The complex transports charge through space via a hopping process. The extensive experimental investigations indicate that exposure to visible light increases electrical conductivity compared to dark conditions, popularly known as PSBD behaviour. The complex conductivity function substantiates the DFT-based DOS, PDOS, and OPDOS plot analysis. Therefore, the heteronuclear complex has been successfully used in thin-film active devices despite technological challenges.

Synthesis And Characterization of Two New Hofmann-Type-Like Compounds From Some Alkali Metal Atoms And Glycine Anhydride

In this study, two new compounds with their closed formula, C8H10K2N6NiO4, and C8H10Na2N6NiO4, were synthesized, the first in crystal form and the second in powder form. Various properties of these compounds were characterized by SC-XRD and FT-IR methods. Theoretical information about the compounds was obtained with the help of the Gaussian 03 program. The molecular formula that best reflects the structural properties of this first 3D compound, which is in crystalline form and has polymeric properties, can be given as {K2(GA)(H2O)2[Ni(CN)4]}n. With a similar thought, it can be suggested that the molecular formula that best reflects the structural properties of the second 3D compound in powder form and with polymeric properties will be {Na2(GA)(H2O)2[Ni(CN)4]}n. The asymmetric unit of the {K2(GA)(H2O)2[Ni(μ4-CN)4]}n compound is composed of a half Ni(II) ion, one K(I) cation, two cyanide ligands, a half GA ligand molecule, and one bounded water ligand molecule. The structure of the compound, which consists of 3D polymeric chains, is formed by various bonds between the GA molecule, K(I) cations, water ligand molecules, and Ni(CN)4 ions.

Crystal structure, Hirshfeld surface analysis and DFT study of N-(2-nitro-phen-yl)male-imide.

The title compound [systematic name: 1-(2-nitro-phen-yl)pyrrole-2,5-dione], C10H6N2O4, crystallizes in the monoclinic system (space group P21/n) with two mol-ecules in the asymmetric unit, which are linked by C-H⋯O hydrogen bonds. Hirshfeld surface analysis showed that the most significant contributions to the crystal packing are from H⋯O/O⋯H, H⋯C/C⋯H and H⋯H inter-actions, which contribute 54.7%, 15.2% and 15.6%, respectively. A DFT study was conducted using three different levels of theory [(B3LYP/6-311+G(d,p), wB97XD/Def2TZVPP and LC-wpbe/6-311(2 d,2p)] in order to determine the stability, structural and electronic properties of the title mol-ecule with a view to its potential applications and photochemical and copolymer properties.

Characteristics of truncation resonances in periodic bilayer rods and beams with symmetric and asymmetric unit cellsa).

Truncation resonances are resonant frequencies that occur within bandgaps and are a prominent feature of finite phononic crystals. While recent studies have shed light on the existence conditions and modal characteristics of truncation resonances in discrete systems, much remains to be understood about their behavior in continuous structures. To address this knowledge gap, this paper investigates the existence and modal characteristics of truncation resonances in periodic bilayer beams, both numerically and experimentally. Specifically, the effect of symmetry of the unit cells, boundary conditions, material/geometric properties, and the number of unit cells are studied. To this end, we introduce impedance and phase velocity ratios based on the material and geometric properties and show how they affect the existence of truncation resonances, relative location of the truncation resonances within the bandgap, and spatial attenuation or degree of localization of the truncation resonance mode shapes. Finally, the existence and mode shapes of truncation resonances are experimentally validated for both longitudinal and flexural cases using three-dimensional (3D) printed periodic beams. This paper highlights the potential impact of these results on the design of finite phononic crystals for various applications, including energy harvesting and passive flow control.