Abscopal Effect, From Myth to Reality: From Radiation Oncologists' Perspective

The abscopal effect is mediated by a systemic anti-tumor immune response and reflects the regression of non-irradiated metastatic lesions at a distance from the primary site of irradiation. This review will focus on understanding the biological rationale behind the abscopal effect of radiotherapy (RT), which has a recently renewed interest as a result of the successes achieved with immunotherapy and RT in combination. Both RT and immunotherapy are standard components of modern treatment regimens. Combination of these two modalities results in an increased response in the irradiated lesions themselves and the metastatic regions distant from the site of irradiation. We will summarize the abscopal effect of radiotherapy, in particular, the synergistic effect of RT and immunotherapy.

The Synergistic Effect of Immune Checkpoint Blockade and Radiotherapy in Recurrent/Metastatic Sinonasal Cancer

Treatment options for recurrent/metastatic sinonasal cancer (RMSNC) patients are limited. We present two cases with RMSNC treated with a combination of immune checkpoint blockade and hypo-fractionated stereotactic radiotherapy (HSRT). 

Case 1 presented with RMSNC three months after the primary treatment. The patient progressed under first-line chemotherapy and pembrolizumab was offered. The disease progressed after the sixth cycle. We performed reirradiation with HSRT to the primary site. Case 2 presented with local recurrence eight years after the primary treatment for maxillary sinus cancer. He refused surgery and chemotherapy and was offered nivolumab treatment. After two doses, we performed reirradiation with HSRT.

Case 1 showed regression at both the local and the metastatic sites after radiotherapy. The second patient’s symptoms resolved completely three months after radiotherapy.

The HSRT and immune checkpoint blockade combination is a promising treatment option for patients with RMSNC.

Crystal Structure and Magnetic Properties of a Binuclear Copper(II) Complex Bridged by an Alkoxo-oxygen Atom and an Acetate Ion

[Cu4(L)2(O2CMe)2] H2O (L = 1,3-bis(5-bromo-2-hydroxybenzylidene)propan-2-ol) was synthesized and its crystal structure determined. (C38H34N4O10Br4Cu4)·H2O, monoclinic, space group P21/c, a = 21.072(5), b = 9.673(2), c = 21.934(4) Å, β = 109.73(2)°, V = 4208(2) Å3, Z = 4. The crystal structure consists of two independent binuclear copper(II) complexes and the non-coordinating water molecule in the asymetric unit. The Cu(II) ions are in a square-planar geometry and coordinated by donor atoms of the ligand (NO3).

The average Cu···Cu distance and average Cu-O-Cu angle are 3.491(2) Å and 132.0(1)°, respectively. Temperature-dependent magnetic susceptibility measurements of the complex show an intramolecular anti ferromagnetic coupling in the dimeric Cu(II) core. The fitting parameters are -2J = 174.4 cm-1, g = 1.98.

Importance of Orbital Complementarity in Spin Coupling through Two Different Bridging Groups. Synthesis, Crystal Structure, Magnetic Properties and Magneto-Structural Correlations in a Dicopper(II) Complex of Endogenous Alkoxo Bridging Ligand with Exogenous Pyrazolate

[Cu2(L3)(3,5-prz)] (L3 = 1,3-bis(2-hydroxy-4-methoxybenzylideneamino)-propan-2-ol) (3) was synthesized and its crystal structure determined. The compound consists of discrete binuclear units, in which copper atoms are linked by the alkoxide oxygen atom of the ligand and the pyrazolate nitrogen atoms. Variable-temperature magnetic susceptibility measurements for a powdered sample of the complex were carried out in the temperature range 4.4 - 308 K and analysed to obtain values of the parameter J in the exchange Hamiltonian H = -2JS1-S2. Recently, the dicopper(II) complexes [Cu2(L1)(3,5-prz)] (L1 = 1,3-bis(2-hydroxy-1-napthylideneamino)- propan-2-ol) (1) and [Cu2(L2)(3,5-prz)], (L2 = 1,3-bis(2-hydroxy-5-chlorosalicylideneamino)- propan-2-ol) (2) were reported. These compounds show antiferromagnetic behaviour (-2J: 444 cm-1 for 1 164 cm-1 for 2, and 472 cm-1 for 3). The strength of the super-exchange interaction (-2J) of 2 is much less than that of 1 and 3, a result which is difficult to explain in terms of structural factors on the basis of widely accepted criteria. The differences in the magnetic behaviour have been rationalized in terms of the bridging ligand orbital complementary / countercomplementary concept.

Crystal Structure and Magnetic Properties of (2,2'-Dipyridyl)-(2-acetylphenolato)copper(II) Perchlorate

The mixed-ligand dinuclear complex (2,2'-dipyridyl)-(2-acetylphenolato)copper(II) perchlorate was synthesized and its crystal structures determined. The structure consists of a dimeric unit involving a planar Cu2O2 group. The coordination sphere of the Cu atom can be described as an alongated octahedron where the basal plane is formed by the two N atoms of the 2,2'-dipyridyl molecule and the two O atoms of the acetophenon anion. Two apical Cu - O contacts complete the 4+2 coordination of the Cu atoms. They correspond to one of the O atoms of the perchlorate anion and to the O atom of the second unit. Magnetic susceptibility data obey the Curie-Weiss law with θ = -8.1(2) K. The decreasing of the effective magnetic moment from 1.94(8) μB at 300 K to 1.86(8) μB at 70 K and the negative Weiss constant indicate weak antiferromagnetic interactions between the two copper atoms in the dimeric units.

Synthesis, Crystal Structure, and Spectroscopic and Magnetic Properties of a Dinuclear Iron(III) Complex Asymmetrically Bridged by a Phenoxo and a Methoxo Group

A new dinuclear iron(III) derivative Fe2L(OCH3)Cl2 (L = 1,3-bis[N-(5-chloro-2-hydroxybenzylidene)- 2-aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine) has been synthesized, it crystal structure determined and magnetically characterized. The two iron(III) ions are asymmetrically bridged by a phenoxo and a methoxo group and separated by 3.150(2)Å . The magnetic susceptibility of the complex was measured over the range 5 - 349.3 K and the observed data were successfully simulated by the equation based on the spin-Hamiltonian operator , indicating very weak antiferromagnetic coupling between the iron ions with J = −11.3 cm−1. The magnetic and structural parameters of the compound and the nature of the magnetic super-exchange interaction are discussed and compared with data of similar dinuclear iron(III) complexes.

Magnetic Properties and Crystal Structure of a 3,5-Dimethylpyrazolate-Bridged Binuclear Copper(II) Complex

[Cu2L(prz)] (prz = 3,5-dimethylpyrazole and L = 1,3-bis(5-bromo-2-hydroxybenzylidene)- propan-2-ol) was synthesized and its crystal structure determined. It crystallizes in the orthorhombic space group Pbca with a = 14.160(9), b = 15.109(4), c = 21.298(5) Å, V = 4557(1) A3, Z = 8 . Two copper(II) ions are in a square-planar coordination. The metal coordination sphere is four-coordinate, with a planar N2O2 donor set. The dihedral angle between the two coordination planes is 12.14(7)°. The copper(II) centers are separated by 3.365(1) Å and antiferromagnetically coupled (J = -214.3 cm-1), which follows from temperature-dependent magnetic susceptibility measurements in the temperature range 4.6 to 310 K. The Cu-O-Cu angle is 125.9(1)° in the super-exchange pathway. The magnetic moment at 310 K is ca. 1.76 B.M. and 0.13 B.M. at 4.6 K.

Crystal Structure and Magnetic Properties of a (μ-Hydroxo)(μ-acetato) Dicopper(II) Complex

[Cu2(L)(O2CMe)] · H2O (L = 1,3-Bis(2-Hydroxy-1-napthylideneamino)propan-2-ol) was synthesized and its crystal structure determined. (C27H23N2O5Cu2).H2O , monoclinic, space group P21/c, a = 11.795(3), b = 17.988(5), c = 12.005(6) Å, β = 109.99(3)°, V = 2393(2) Å3, Z = 4. Two copper(II) ions in a square-planar coordination are bridged by alkoxide and acetate oxygen atoms to form a dinuclear unit. The metal coordination sphere is four-coordinate, planar with an NO3 donor set. The dihedral angle between the two coordination planes is 6.34(9)°. The copper(II) centers are separated by 3.492(2) Å and weakly antiferromagnetically coupled (-2J = 163.6 cm-1 ), which follows from temperature-dependent magnetic susceptibility measurements in the temperature range 4.6 to 310 K. The Cu-O-Cu angle is 133.5(1)° in the super-exchange pathway. The weak antiferromagnetic coupling of the complex is interpreted in terms of countercomplementary effects of the different bridging ligands which participate in the super-exchange interaction. The magnetic moment at 310 K is ca. 2.7 B. M., but 0.2 B. M. at 4.6 K. The magnetic susceptibility is at a maximum near 140 K and decreases rapidly as the temperature is lowered to liquid helium temperature.

The Synthesis, Crystal Structure and Spectroscopic Properties of a Dinuclear μ–Pyrazolato–N,N’–Bridged Dinickel(II) Complex of 1,3–Bis(salicylideneamino)propan–2–ol

The title compound [Ni2(L)(3,5 prz)], prz = pyrazolate with the formally pentadentate ligand L = 1,3-bis(salicylideneamino)propan-2-olate, was synthesized and identified using elemental analysis and IR spectroscopy. It crystallizes in the monoclinic space group P21/c with cell parameters a = 29.873(4), b = 11.131(2), c = 13.166(3) Å , β = 107.770(10)°, V = 4169.0(13) Å3, Z = 4, Dcal = 1.618 Mg/m3. The nickel ions are bridged by the alkoxo group of the ligand and the N atoms of the μ-pyrazolate group. Each nickel(II) ion is coordinated by two N atoms and two O atoms, forming a square with trans-N2O2 geometry. The Ni···Ni distance and the Ni−O−Ni angle are 3.371(1) Å and 126.4(1)°, respectively.

Crystal Structure and Conformation of 2-{(2′-Aminobenzyl)iminoethyl}- 5-methoxyphenol

The Schiff base, 2-{(2′-aminobenzyl)iminoethyl}-5-methoxyphenol, 1,2 -C6H4[NH2-2 ʹ]-CH2N=CHC6H3(OMe-5)OH (I), has been prepared by the reaction of 2 -amino-1-benzylamine and 2-hydroxy-4-methoxyacetophenone in methanol. The molecular structure has been con­firmed by single crystal X-ray crystallography (triclinic, space group P 1̄, a = 7.201(2), b = 9.802(2), c = 9.993(2) Å, α = 83.09(2), β = 73.49(2), γ = 84.09(2)°, R = 0.0415 for 2611 independent reflections). The 1H and 13C NMR spectra in CDCI3 solution indicate the forma­tion of some other minor conformations or dissociation in solution. The title compoundois not planar. Intramolecular hydrogen bonding occurs between O(1) and N(1) atoms [2.528(2) Å], the hydrogen atom essentially being bonded to the nitrogen atom. Minimum energy conformations from AMI were calculated as a function of four torsion angles. The optimized geometry of the molecular structure corresponding to the non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded hydrogen-hydrogen repulsions.

The Synthesis and Crystal Structure of a Dinuclear μ-Pyrazolato-N,N'-Bridged Dinickel(II) Complex of 1,3-Bis(2-hydroxy-4-methoxybenzylideneamino)propan-2-ol

Ligand The asymmetric unit of crystal of the title compound, [Ni2(L)(C3H3N2)] (L = 1,3-Bis(2-hydroxy-4-methoxybenzylideneamino)propan-2-ol, C3H3N2 = pyrazolate) contains two inde­pendent dinickel(II) complexes. In both molecules, the nickel(II) ions are bridged by the alkoxo group of the ligand and the N atoms of the pyrazolate group. Each nickel(II) ion is coordinated by two N and two O atoms, forming a square with trans-N2O2 geometry.

Crystal Structure and Magnetic Properties of a New Hetero-Dinuclear CuIIMnII Schiff Base Complex

Mn[Cu(L)(O2CMe)2] · H2O (L = N,N’-bis(2-hydroxy-3-methoxybenzylidene)-1,3-diaminopropane) was synthesized and the crystal structure determined. (C23H26CuMnN2O8).H2O, monoclinic, space group P21/c, a = 12.017(3), b = 8.217(3), c = 24.786(4) Å , β = 92.10(2)°, V = 2446(1) Å3, Z = 4. The crystal structure consists of ordered dinuclear units with CuII and MnII ions bridged by two oxygen atoms of the Schiff base ligand. The CuII coordination sphere is a slightly distorted square-plane formed by the N2O2 donor set of the Schiff base ligands. The average Cu-O and Cu-N distances are 1.920(1) and 1.957(4) Å , respectively. The coordination around the MnII ion is a distorted tetrahedron with the donor oxygen atoms of the Schiff base ligands and oxygen atoms of the acetate anions. The Cu ··· Mn separation is 3.327(4) Å . There is also one non-coordinating water molecule in the crystal structure. The χ and χT versus T plots, χ being the molar magnetic susceptibility per CuIIMnII unit and T the temperature, has been measured in the 4.9 - 301 K temperature range. The values of the interaction parameters are J = −28.3 cm−1, gMn = 2.01, gCu = 2.07. This indicates an intramolecular antiferromagnetic interaction between CuII and MnII ions.

Crystal Structures and Magnetic Properties of (2,2'-Dipyridyl)-(3-methoxysalicylaldiminato)copper(II) Perchlorate and (2,2'-Dipyridyl)-(4-methoxysalicylaldiminato)copper(II) Perchlorate

The mixed-ligand dinuclear complexes (2,2'-dipyridyl)-(3-methoxysalicylaldiminato)copper( II) perchlorate (1) and (2,2'-dipyridyl)-(4-methoxysalicylaldiminato)copper(II) perchlorate (2)were synthesized and their crystal structures determined. Both structures consist of a dimeric unit involving a planar Cu2O2 group. In both structures, the coordination sphere of the Cu atoms can be described as an elongated octahedron where the basal plane is formed by the twoN atoms of the 2,2'-dipyridyl molecule and the two O atoms of the salicylaldehyde anion. The phenoxo O atom is the negative ligand of the monomeric unit. Two apical Cu-O contacts complete the 4+2 coordination of the Cu atoms. They correspond to one of the O atoms of the perchlorate anion and to the O atom of the nearest salicylaldehyde molecule. Variable-temperature magnetic susceptibility data obey the Curie-Weiss law with Θ = -10.3(2) K for 1 and -10.1(2) K for 2. The decrease of the effective magnetic moment from 1.89(7) μB at 300 K to 1.77(7) μB at 70 K for 1 and from 1.88(8) μB at 300 K to 1.76(8) μB at 70 K for 2 and the negative Weiss constants indicate weak antiferromagnetic interactions between the two copper atoms in the dimeric units.

Synthesis and Crystal Structures of a New μ-Bis(tetradentate) Schiff Base Ligand and its Mononuclear Iron(III) Complex: Iron(III) Induced Imidazolidine Ring Hydrolysis of Binucleating Schiff Base Ligand

The μ-bis(tetradentate) ligand, [C27H26Cl3N4O4], H3L′, 1,3-bis[N-(5-chloro-2-hydroxybenzylidene)- 2-aminoethyl]-2-(5-chloro-2-hydroxyphenyl)imidazolidine and its mononuclear iron(III) complex, [Fe(L)](ClO4), L = N, N′-bis(5-chloro-2-hydroxybenzylidene)-triethylenetetramine have been synthesized and their crystal structures determined. Minimum energy conformations of the ligand were calculated (MOPAC, AM1) as a function of two torsion angles and the results compared with optimized crystal structure. The ligand (H3L′) reacts with Fe(ClO4)2 · 6H2O in aqueous methanol to form the mononuclear [Fe(L)](ClO4) complex with the imidazolidine ring cleaved by hydrolysis. The complex has an N4O2 donor atom set forming a distorted octahedral coordination geometry around the metal atom as established from a crystal structure determination. The terminal oxygen donor atoms occupy cis positions, and the remaining four nitrogen atoms (two cis amine and two trans imine) complete the coordination sphere.

Magnetic Properties and Crystal Structure of a Dinuclear Iron(III) Complex

[FeL(MeOH)Cl]2 (L = N-(5-methylphenyl)-3-methoxysalicylaldimine) was synthesized and its crystal structure determined, [C30H26Cl2Fe2N2O6], triclinic, space group P1̄, a = 7.481(2), b = 9.436(2), c = 10.961(2) Å, α= 69.790(10), β= 82.440(10), γ= 83.690(10)°, V=718.1(3) Å3 , Z = 1. Two identical [FeLCl] fragments, related by an inversion centre, are connected by two bridging O atoms to form a binuclear unit. The iron(III) centers are separated by 3.196(2) Å and weakly antiferromagnetically coupled (J = -10.4(1) cm-1), which follows from temperature-dependent magnetic susceptibility measurements in the range 5.1 to 275.6 K. The magnetic moment at 275.6 K is ca. 7.02 B. M., but 0.99 B. M. at 5.1 K. The magnetic susceptibility is at a maximum near 80 K and decreases rapidly as the temperature is lowered to liquid helium temperature.